The stuttering is caused by peaking CPU cycles. If you run a CPU meter during gameplay, then alt-tab out, you'll see that the CPU is at 100%.
If you have Vista or Win7, then there is a tweak you can do to make the game more playable. You still get the stuttering, but it is hardly noticeable.
-Run Windows Task Manager
-Start the game and leave it at main screen
-In Task Manager(under the processes tab), right click the Divinity2.exe, and set priority to high.
-Alt+Tab back to the game and play.
Also turn on Timeslice Shadow updates.
The game may hang when you exit out, so you may have to kill the process manually.
