I've been getting this since the pre day zero version, and I have a friend who seems to be getting it as well.  I'm not sure if it's tactical battle related or what, but after a while the game experiences a lot of slowdown.  The game itself gets pretty choppy, but the shop, diplomacy, and post battle/level up screens are really what become unbearable.  The strange thing is that the game doesn't crash (no OOM messages or anything) and restarting doesn't help.  Even if I restart, the opening movie and main menu are extremely choppy, and a computer reboot is needed to fix the problem.  Recently, I tried avoiding tactical battles as much as possible, but it still occurred.  Also, though this may be my imagination, it seems that saving before/after tactical battles exacerbates the problem, but I can't be sure.  I'd be happy to try different settings, they are mainly default at the moment.  Here is my latest debug file.  Thanks.

http://pastebin.ca/1927056