While I understand the benefits of sniping (I do it quite often, I just do it manually as I don't bid on tons of stuff), in the majority of cases stuff tends to be bid higher by other folk first, so any benefit sniping would have given me disappears due to the back and forth of a few people. I have had some successes, but I can't quite say whether anyone would have bid higher on those auctions anyway.
Your best bet with sniping is to bid on stuff that is less popular, as there will only be one or two bidders. On popular stuff, say mordheim auctions, oop empire stuff, etc, the bidding is most often higher than I want to bid before the end anyway (hence my disenchantment with sniping).