I just read a blog with all the tips about this site. I would highly recommend doing that. I'll look for the link. Basically its legit. I'm not sure it should be legal, but if you prepare yourself you'll do fine. #1 rule I took away, only bid on things you actually want and will pay full price for. That ways you minimize your risk in a big way.
They offer a Buy It Now option on most items. If you expend too many bids, or are running out of time, you can use all you "used" bids real value to buy it now at retail. This means you don't lose the money you spent on bids.
There are voucher bids which cannot be used for buy it now so they have less value. Do your homework and you might get a good deal by having some uninformed gamblers pay for your Ipad.