I'm going to agree with Pete, when everything is in good order the bike runs well and won't let you down. The problem is, most of the 400s have been parked somewhere for a few year and there are a few parts not in 'good' order, usually carburators and electrics.
Electrics can usually be taken care of by going through each connection, cleaning it, and making sure it's tight. Short of replacing the wires, thats about all you can do.
The carburators are another story altogether. Even when cleaned and in good shape, the carbs can be finicky. I've never been stranded by my bike (well, I did run out of gas once, but that was my fault). Mechanically I don't think your going to find a better bike for the money, but like Pete says, parts are hard to find.
The GS500E is also a really nice little bike, mechanically a lot less complex than the Bandit since it's an Air-Cooled twin. Half the cylinders means half the parts to break, half the carbs to tinker with, and the air cooling means you don't have to worry about the fan, radiator, and hoses.