I've had some right bargains by firing in last second bids on Ebay - it is the only way I buy on there now, I don't see the point in bidding 6 days before the end for the price to be bumped up
Only downside is you have to be prepared to pay a little over the odds sometimes if it is something you want that isn't available else where as your 5 second bid might not be high enough to kill off the competition