Before I write my impressions from the demo I just wanted to give my rig, as I was afraid I wouldn't be able to run M2:TW.
Pentium 4, 2,66 GHz
1024 MB RAM
Nvidia Geforce4 Ti4200

I ran it on medium settings and everything was smooth as hell. Looked ugly too, especially the units with bad textures and all blurry. So I manually changed those settings and it looks and plays nice now. Good that I can put off my computer upgrade a little longer and not have M2:TW force me to do it.

Cheers!

Ituralde