The trip from Lima to Ayacucho — 9 hours overnight — was my first-ever luxury long-distance bus journey. Much nicer than the comfortable, but not lavish, 1st class buses in Mexico. I went with Cruz Del Sur, one of Peru's top bus companies. Seats that reach back all the way. Large, padded footrests. Tea / coffee and sandwiches served in-trip. And a few movies along the way. Not quite up there with what I've heard about the super-luxurious coaches in Argentina, but impressive nonetheless.
The bus was a double-decker, and I was on the bottom level. I had a great night's sleep, and didn't feel sick at all along the way; but Cath and Gaz, who were at the top level, said that they were feeling nauseous the whole way, and that they got hardly any sleep. I guess that the bottom level is better!