Memory leak in X? Shocking!
I've been dealing with (slower) memory leaks in X for months now, mostly by ignoring them and hoping they'll go away. It tends to limit my uptime to ~30 days, if I'm willing to deal with running a reduced set of apps for the last week. Right now my desktop at work is using 1 out of 4GB for X, and at home it's at over 3.5 of 8GB. Happening on two different distros with different video drivers and different versions of X, so I rather assume it's not due to some uncommon combination of circumstances. And no, closing things doesn't make X release memory, I've got to kill X entirely, which, screen sessions aside, might as well be a reboot.
Since I'm so stubborn, I'm going to go ahead and blame it on all the X development that (I imagine) is wasted on features so unimportant as jiggling windows and "Oh look it's raining on my desktop!"
I haven't noticed any improvement in my user experience from X since they went with the modular version, which I believe coincided with Canonical taking over development...