I' m using Quarls texture pack, you definitely have to live with some stuttering every time the game loads new areas.
the framerate for me in general is about 40, sometimes it can drop to 35 depending on where i am...
System:
AMD Athlon x2 965 be (Quadcore@3,6 ghz)
4 gb ram
hd 5850 1gb slightly oc
1680x1050, all settings maximum.
if you have an ssd, you could try to install it there, according to an older post (forgot where, sorry) this dramatically reduces
stuttering while loading new areas. will try it myself in the next days and post the results.
when i installed the game i didn' t have enough free space on my ssd.
anyways, If your pc can take it, i would definitely go with quarls textures, the improvement is worth it!