I have the M6500 laptop with Windows 7 and use Houdini but not renderman. The program runs well but one factor you may want to consider is the latop has a serious design flaw (for me). The laptop has very sharp corners and because of the way the keyboard is positioned (not in center because it has a 10 key pad in addition to QWERTY) your left wrist hits the sharp corner and over time it is really annoying to be stabbed by your laptop... after paying almost $6K!
I urge you to look at this carefully before buying. Good luck.