A few months ago I purchased a Linksys WRT-54GL hoping to decrease my power usage without losing too much functionality. I very quickly went to DD-WRT and found it to rock. I'm very happy with it and likely won't upgrade unless of a severe critical bug.
I did, however, find one setting incredibly useful when dealing with torrents: Adjust your TCP timeouts. I adjusted my TCPto be 120 (TCP is defaulted to 3600 while UDP is 120 already). This way, when you turn off your torrent app, in 2 minutes all those connections die off.
The main benefit for this is if you game and you want to game NOW, you don't have to wait too long before your lag issues go away. Another main advantage is that it helps prevent connection overload -- which is why most routers lock up after a few weeks and you have to reboot them, if you torrent.
Given the quantity of torrenting I do, uploaded ~ 1TB of data, I really liked this.
Maybe one day I'll drop some testicals and do some hardware hacking on the thing.