Initially with 0.13.2 (the first release I tried on Titan Quest) the game ran fine, except for when I opened a UI window (inventory, map, quest dialogue, etc) and the framerate slowed to a crawl, but only for the duration of the window's existance. Now, with 014.0, the framerate goes down without the need of any UI windows open, and then gets even worse (to the single digits) with a window open.
Here's the tracelog.