Like will says, check the feedback and get a feel for the trustworthiness as best you can.
I've bought 2 guitars, roto toms (drums), cymbals (for drums), currently waiting to recieve my newest drum, albums, CD's, books, I get my printer inks there and at a WAY cheaper price than at stores, software, videos, my digital camera...get the picture? Only time I got burned was buying a record turntable from some Canadian! lol
Best use of ebay IMO though is comparison shopping.