Used it several times, and never had a problem. We got a week at Orange Lake Country Club for $265 total. Also got some airline tickets to London for $800 less than they were selling at any other web site.
Some tricks:
1. Make sure you are aware how much the final cost will be. The bids look low, but they add mandatory charges. The above week at OLCC for $265 was actually a $50 bid.
2. Make sure you compute the extra charges right. Sometimes they make it look less by showing what the charge will be "per person based on double occupancy" or "per night" or even "per person per night."
3. Don't get stuck on any single auction. Look around and see if there are other auctions for the same thing that are getting less bidding action. This is especially true for the time share weeks they sell.
4. The best thing about skyauction.com (as opposed to priceline or others) is that you have no obligation to pay if they can't give you what you want. If the flight times or anything else they send you doesn't work for you, ask for changes. If they can't accomodate you, the auction is cancelled, no problems.