I have had the best luck w/ used instruments, bass and acoustic 6-strings. Sure you have to look carefully at a used instrument. If you buy one, make sure you can take it back during a set try-out period. During that period have a luthier take a look at it.
For one thing, the wood has opened more on a used instrument. Maybe not so much a factor on a solid body but for a hollow or semi-hollow body this is a factor.
In the current economy, sad to say, many musicians are selling instruments not because there is something wrong with the ax or they want to, it is because they have to. And many dealers are really dealing and accepting offers they normally would not have. So now is a good time to go for a used instrument if it is one you really want.