1. What one thing you wish you had brought from US?
When I first started my trip, I wished I had brought some warm clothes. I figured Peru was near the equator, so it would be hot all the time there. I didn't even bring a long sleeved shirt. That plan backfired bigtime. Most of my time in the country was spent at high altitude, where it got really cold at night, so I had to buy a bunch of warm clothing while I was there. Still, I think I only spent about $15 for a shirt, gloves, hat, and scarf, so it wasn't that bad.
Sometimes I wish I had brought some camping gear, but then I realize that I would only have used it for maybe two weeks out of my whole trip, so it wouldn't have been worth it.
This list is small, which taught me an important lesson about traveling: I can easily buy just about anything from anywhere in the world without much trouble, and other than electronic equipment, it will probably be much cheaper than in the US. Therefore, it's better to start out with only the stuff you know you'll use and acquire the little things you didn't think to bring after you're there and you know you'll use them.
2. What things you should not have brought?
Luckily, this list was really small for me too. I was surprised to find that I didn't use my binoculars at all. I thought they would come in really handy, but every time I wanted to see something far away, I just used my camera's telephoto lens. The other thing I regretted bringing was my walking stick/monopod. I never used it as a monopod because I found that the best time to use a monopod is when shooting sports, which I haven't done yet. I almost never used it as a walking stick because it didn't seem to help me much, although I must point out that a lot of other people find using one or two sticks very useful when trekking. I ended up sending both items back home after I was gone for three months.
3. What one thing are you most glad you brought?
Of course I'm glad I brought some underwear, but that's probably not what you meant. For items that I considered leaving behind but still ended up bringing, I'd have to say my laptop and my SLR camera. I know that's two items, but I just can't see my trip being even remotely similar to what it's been so far without either of them. I use my laptop nearly every day to update my blog and look at photos. I don't use my SLR camera quite as often, but I've taken around 15,000 pictures with it since leaving, many of which simply would not have been possible with a small point and shoot camera.
4. Night scene?
Argentina easily has the best night scenes I've ever experienced. Restaurants don't even open until 8:00 PM here, and most people don't eat until 10. Steak seems to be the national religion here. You can get a huge cut of whatever type of meat you want at any restaurant, and it has a reputation for being the best beef in the world. The best part is that a steak meal in a restaurant can cost as little as $5. Red wine is almost always served with dinner, and it's some of the best wine in the world. I think the only reason Argentine wine hasn't gotten a better reputation is that the local people drink so much of it that there isn't much of a need to export it.
The culture is so laid back here that people don't go out to clubs until 1 or 2 in the morning. I don't even know when they close here yet because I usually want to go to bed by 7:00 AM, when the clubs are still going strong. The other thing is that anyone from 18 to 70 can go out at all hours of the night and have a good time without feeling too old or young.
One downside of Argentina is smoking. I think everywhere I've ever visited, people smoke more than in the US, but it's taken to another level here. People smoke in bus stations, shopping malls, Internet cafes, beauty salons, and basically wherever else they want to. Cigarettes only cost 63 cents per pack here, so I guess I can see why it's so popular. It's definitely not a good place to go if you want to quit.
6. How are bars, clubs,disco (Whatever they call them there)
This goes along with the night scene question, but the clubs, discos, or boliches (people use all 3 names, but the last one is the funniest because it means "bowling alley" in Mexico) are great. They don't get going until 2:00 AM and stay open until everyone leaves, which seems to be never. Drinks are usually expensive ($2-3 per mixer), so most people just go there to dance. The drinking age is 18 here, just like most of the world, which means that a lot of young people go out late. Still, people of all ages go to the clubs here.
7. Just curious, have you run into people/back packers from countries other than Western Europe, Australia/New Zealand and US?
You listed most of them, but a few other common ones are Canada, South Africa, Japan (although most aren't backpackers), and especially Israel. Everywhere I go, I run into a lot of Israelis. In Israel, military service is required for men for 3 years and women for 2, and when they get out, they almost always travel somewhere. It seems like half of Israel is in South America now. They usually travel in large groups, and even though they all speak English, it's really hard to break into their social circles. At hostels, there are the Israelis and Everyone Else. However, I should point out that the few Israelis I've met who were traveling alone were nice and more social with non-Israelis.
I also meet a fair amount of people from other Latin American countries like Mexico, Chile, Brazil, and Argentina. In Argentina especially, I meet a lot of Argentines. They understandably love traveling around their own country, and it's summer here, so a lot of people have vacation time. In Buenos Aires, I think I met more Brazilians than any other nationality.
9. Are you sick of traveling yet?
No, I don't think it's something I'll ever get sick of. I like to take a few days to relax every now and then, but I always get a feeling of adventure whenever I go somewhere new. In fact, I think I'm just getting started with the whole traveling thing. It might be nice to take a small break and head back home for awhile at some point, though.
10. What is the difference between Argentina and Patagonia?
Patagonia isn't a country. It's the name for the area at the south of both Argentina and Chile. Where Patagonia begins is debatable. Chileans usually say that it begins after the island of Chiloe, and Argentines think that it starts around Bariloche, which is much further north. Sometimes Tierra del Fuego, the chain of islands at the bottom of the continent, is considered part of Patagonia, but usually it isn't. So when I mention Patagonia, I'm really just talking about southern Chile and Argentina, but I don't want to keep repeating the same words over and over.
11. Machu Picchu - How far did you walk each day on the hike in?
The total walk was about 40 KM and lasted four days. Day 1 was easy because most of it was spent driving to the start of the trail. I think we only hiked for about 4 hours with frequent breaks. Day 2 was the hardest because we had to cross the First Pass, which was at around 4200 meters altitude if I recall correctly. We probably walked for a total of about 8 hours that day. Day 3 took ten hours or so, but it was easy walking for the most part. Day 4 took only about 2 hours to walk from camp to Macchu Picchu and was very easy. Once we got there, we had a walking tour that lasted about 2 hours, but it took about 6 hours for me to see the whole complex.
If you're asking this question because you're thinking about doing it and want to know how challenging it will be, it is fairly tough, but very rewarding, and you can probably do it even if you're not in great shape. The biggest issue is the altitude. It's very important to rest in Cusco for a few days before beginning the Inca Trail so you have some time to get acclimatized. If you don't like the idea of carrying 20 pounds of gear with you, you can hire a personal porter to carry your stuff so you'll only need to carry a camera and a bottle of water. The guides are very patient with people who need extra time, so as long as you are in decent shape, it will be challenging, but not impossible.
Another option to see Machu Picchu is to take the train directly there from Cusco. A lot of the backpackers I met did this because it is a lot cheaper than hiking the Inca Trail. I'm still glad I took the Trail, though. I got to see ruins along the way and learned about the Inca culture from a knowledgeable guide. I think this added to the experience of seeing Machu Picchu because I knew what it, and the people who built it, were all about. It also gave me a sense of accomplishment because after 4 days of hiking, I was rewarded with the biggest and most beautiful ruins site I have ever seen, while the people who took the train didn't have to do any work to get there.