I use:
http://esnipe.com/
Some advantages:
If you want to bid at the last minute, then you don't have to stay up until 3AM groggily poised over your machine watching the clock go down 8 seconds, 7 seconds, 6 seconds. etc. until the auction ends.
By putting a proxy bid in on eBay during the listing, you're actually encouraging clueless bidders (and there are a lot of them) to keep bidding up your proxy. So it's entirely possible that you'll be paying more than you would have if you just kept silent and out of it, and came in at the last second or two.
You possibly could still be outbid (and often will be) with a snipe by a higher snipe, or even someone's proxy that will go up when your snipe bid hits the system.
But if you put in your HONEST highest-you're-willing-to-spend amount for the widget, then it's gonna end however it's gonna end.