This is an addition to the post: 6 Useful Tips for Travelling with a Bus in South America.
Buses in Perú
In Perú I mostly travelled with Cruz del Sur. It is more like travelling with an airplane than a bus ride from the organization and safety features. At least if you take the first two classes. I travelled with all three classes, between the first (Cruzero) and second class (Imperial) there is only a slight difference. The third class (Ideal) is also really good, but it depends where you travelled before and what you want. The first two classes do non-stop travel (with on-board breakfast/lunch/dinner), thus you don’t even have to think about your backpack on the whole ride.
I only travelled with Cruz del Sur in Perú, thus I don’t know anything about the other companies. I heard that Cruz del Sur is overrated, but this was from a female backpacker who travelled Bolivia on her own for a few weeks, thus she was well experienced and hardend than most other backpackers out there.
Note, when you travel with the first two classes of Cruz del Sur that the passengers are mostly higher middle-to-upper class Peruvians and tourists.
Buses in Chile and Argentina
Good quality, good service and secure. It is the common way to travel for most people in these countries and it is also quite cheap for them. In Argentina have a bit of tip ready for the person who takes out the backpack of the bus and checks your voucher. I think 0,25 to 0,50 Pesos were common, just take a look what the other people give him.
Buses in Bolivia
Bolivia is always a great adventure and so are the buses and the roads. The buses are not really comfortable, cleanliness is limited and I watched my stuff very closely. Especially, since the country is very poor and I am really rich compared to nearly everyone there. I always boarded the bus after I took a look, where my backpack was stored and that most other people boarded the bus. Also I couldn’t determine a difference between most bus companies in less touristic areas. Only in Salar de Uyuni there are one or two special agencies that provide high quality buses, I don’t know the names but it is quite easy to find them.
Another thing, the leaving times are quite strange. When I was in Tupiza (Southern Bolivia), I needed a ride from there to Sucre, well all companies were leaving at the same time to Sucre and they did it only once a day!? Thus, it is better to check beforehand. Don’t assume – like I did – that they each company leaves at another time.
For further information about traveling with a bus or specific routes, I would recommend the following books. These are made by backpackers for backpackers and contain loads of information in a well organized manner. I can highly recommend them.