Well I'm using 169.38 with Vista Ultimate. There isn't much difference as far as general gameplay performance between dx9 and dx10. The first 2 screenshots are in Bree. Loading all the players and npc's in will drop fps to high teens. General grinding and running around 50 fps. No crashes so far with about 2 hrs of playtime last night.
dx10 performance for lotro:
1280x1024 4xAA 16xAF