I've bought a fair amount of bike gear on Ebay. You can find jerseys and jackets at good prices slightly use, I've bought several jerseys for under $10 like new. I DON'T buy used shorts, tho.
I try and stick with sellers that have perfect feedback, preferably on hundreds of transactions. No problems so far. I see it(ebay) as just another means, along with LBS and mail order, to feed the REAL addiction (cycling).