I used to use auction sentry, but I jumped ship a little before he did. The major advantage of AuctionSniper over AuctionSentry is that you don't have to depend on your own hardware/connection. It also has several tools to allow you to do nifty things like place snipes on a group of auctions and stop after you've won a certain amount, so if you want an item you can find all of the auctions and group them and stop after you've won one or something like that. Also, it's easier to add auctions in my opinion. Of course, the downside is that you pay when you win using AuctionSniper, but I've even done such things as bid normally on an item, then snipe it... if I win with my bid, I don't get charged. I really like it.