took buses in Venezuela, Peru, and Bolivia. It can go from awesome to down right scary and insane. Depends a bit on the route. Major route between 'major' city centers, generally a fancy bus that is pretty damn plush and they make great time. Going somewhere a little more out of the way -- you get a greyhound equivalent bus. Somewhere really out of the way? a really really janky old thing that god help you stays on the road as it speeds around corners at 10,000ft in the rain.. Hmm.. in 2 months in Venezuela had a bus break down twice. Then again we took perhaps 10 or 15 buses in that time.. once was on a mountain road and we hung out for about 2 hours, nice views, great stream..washed my hair.. the other time in the middle of the night in the llanos (flat grasslands) hot as hell mosquitos like crazy.. why? because they have bizzare ass roads. I bet there is more miles of roads from the forest service in Oregon and/or Washington than the whole Venezuelan country - and they barely maintain them (bridges out, 2 foot deep potholes..etc--its very entertaining)
also, on the really nice buses, they have air conditioning - but it is permanently set at 50 degrees - seriously, take a long bus trip in Venezuela, take a blanket!