I've had my Thinkpad T420 (integrated graphics, 8GB RAM, i5) for less than a month. I couldn't successfully install Natty (installer finished, but wouldn't boot), so I went with Maverick instead. On a daily basis, it completely freezes at least once, seemingly always when I'm in Firefox with multiple tabs open. My mouse can still move, but nothing is clickable, and I always have to do a hard restart.
I confirmed that this isn't a Unity bug, because I installed 10.10 in "command-line only" mode via the alternate install dvd, and manually installed X-server and fluxbox. The freezing still exists, without Unity or even Gnome running, whenever I do anything mildly resource-hungry in Firefox.
Thanks for any guidance.