I personally don't care one way or the other about the 15 minute rule, I just do as stumps said...I put my bid in and wait. I like to watch the end of the auctions, but I always try to stay within what I think the item is worth to me.
I can however see how this rule could be problematic, and would really pi$$ me off if it ever happened to me.
Let's say that there is something coming up for bid that you wanted pretty badly, and you know you could get it for minimum bid because there are a bunch of them (plus it's not worth any more than the minimum to you). So you put your bid in early, and wait. Now it's 1 minute before the auction closes, you have your lot(s) at the minimum bid and most of the rest are spoken for with minimum bids also (a few have no bids on them at all). Now 5 seconds before the auction ends some jacka$$ comes in and, rather than put a bid on one of the items that has no bid, bids on your item at the last second. This extends the item you wanted by 15 minutes. But at the same time the 4 other items that had no bid on them at all, are now closed and there is no chance of you getting one of them for the minimum.
A situation like this would really make me mad.
I know it's probably never going to happen, but it is an example of how the 15 minute rule could bite you in the a$$.