Ever since I first got my AMD64 box one think always annoyed me - my on-board VIA velocity didn't work with ifplugd or netplug as it always thought there was a cable plugged in. This was less than optimal as with the new coldplug functionality in baselayout it started by default and tried to get a DHCP lease by default.
So I finally got of my lazy rear end and filed a kernel bug. With Francois Romieu I wrote a patch that has been accepted into the mainline kernel :) OK, he wrote the actual fix, but still. It gives a very big warm fuzzy feeling that you've contributed something to the kernel as every Linux user uses it :D
I've also filed a bug requesting the inclusion of the patch in gentoo-sources so hopefully Gentoo users will get the fix a bit quicker :)
The morale of this story is to file a bug if something doesn't work for you as it gets fixed much quicker!