You bid on a particular auction, so you know ahead of time what you are going to win. They will charge you if you win, so you can't change your mind(although I have read of instances where they did let people change their minds)
I bid on the ready set go auctions. Before I bid, I made sure that there was something available where and when I wanted to go. You can usually win these for 50-60. Then add on the fees, and you end up paying about $265 for a week in a 2 bedroom condo.
There is a section at the top labeled 'winners'. You can look on there and see what auctions you are interested in have been won at in the past(they generally run the same auctions over and over again).
Skyauction is a great deal, and I have not had problems with them yet. As far as I can tell, they auction off excess timeshare and hotel space.
The best deals can be found at the 'ready, set, go' auction. I don't think the nightly rentals are usually such a great deal.
There are a few auctions that they have posted that look like they are timeshare deals, but they are labelled that way. Don't bid on those unless you want that kind of deal. You do not have to do a timeshare deal with the regular auctions.
I have won 3 times in Orlando(most of their rentals seem to be there), once in the Wisconsin dells, and a cruise.
Let me know if you have more ?