I have been sniping on eBay for over four years and I have one service that does it all for me. The best a href=http://www.BidSlammer.comsniping service/a of them all is BidSlammer.com hands down.
I have had virtually no problems with the service. Lots of times I thought I missed snipes and their customer service team took great care of me and helped me understand the miss. Their 99.9% accuracy has held up time and again, as I've bid on over 5,000 items with them and had perhaps 1 miss they could not explain.
I also love the bid groups feature, I won my wife's favorite necklace using bid groups. You just place bids across lots of different related items and when you win one, it shuts off the other bids!!! I have scored some great deals.
Also the interface is totally intuitive. You can change all your bids at one time. My grandmother can use BidSlammer. And the SlamIt toolbar is awesome, I never have to leave eBay.
Finally the pricing is awesome, even though they charge a quarter minimum for a win (which might seem high for a $10 item), they FOLLOW THROUGH. I can deposit $10 and use BidSlammer for a year, as opposed to having to spend $60 for a desktop program that I continually have to update it.
Do yourself a favor. try BidSlammer's eBay sniping service. You'll love it.