It's really handy to hold your bids until the last minute, especially useful when bidding on low--cost everyday items you want. Instead of just bidding up the final price, I buy in the last five to 10 seconds of an auction.
I can be anywhere when auction ends, BidSlammer takes care of it for me.
I missed a couple of auctions but due to my own ineptness. I changed my eBay password and didn't update BidSlammer so at the last minute, they couldn't get in. Rats! But you only do that once.