I don't know if I have enough space here to express how impressive this site is.
I've used 5 different auction snipers now and they were all pretty much the same. They were all bland looking and their performance was even more bland.
GavelThief on the other hand is a well made website. Not only does it look great, it performs even better. I've sniped 20 auctions now and of those auctions, I won 14 and lost 6 (I was outbid). Of the 14 auctions that I won, 12 auctions were sniped exactly when I specified (3 second lead time). The other two snipes were places a mere 1 second early. That is absolutely awesome!
As if that weren't enough, the staff are personable and down to earth. I'll give an example. Not long ago, I went to the GavelThief forums and made a suggestion (an effort to prevent an auction from being added twice) and my request was implemented in about 2 hours. Ladies and Gentlemen, that's the definition of customer service. Any other snipers would have taken 2-3 days minimum.
GavelThief also have some great extra features. With the Smart Bidgroups, I can add several items to one bidgroup and create conditional bidding rules. I also really like the SMS text message notifications. I have it set up to send a text message to my cell phone when I am outbid and when an auction ends. In the event I am outbid, I can increase my maximum bid right from my cell phone if I want. Another cool feature is the package tracker. When I win an auction and give GavelThief the tracking number, it automatically detects the courier and displays a map with the location of my package. And last but not least, the Bookmark Sniper is great because I can just browse through eBay and when I find an item I want to snipe I just click the bookmark. It automatically fills in most of the information, I just specify the max bid and lead time.
That being said, it is obvious that GavelThief is the best eBay auction sniper and it's not even close.