It really depends on what you play, and also what your CPU is.
The highest-end game I play on my laptop (T7100/X3100) is Guild Wars - fullscreen, 1280x800. Most places I get 25+ FPS, though it will sometimes dip into the teens in highly-populated areas (e.g. Lion's Arch). With that CPU there's almost no performance difference between hardware and software T&L, although maybe hardware would give it a bit of extra headroom in CPU-limited areas.
Actually, I also play Vampire the Masquerade: Bloodlines on it, which gets 10-20 FPS in the Santa Monica hub, but that's CPU-limited on my E6300/9600GT as well ...
WoW should be fine - its requirements are around the same as GW - maybe a bit lower (although I believe the Wrath of the Lich King expansion allows more-intensive graphics).
The X3100 drivers don't support anti-aliasing at all, which is quite annoying because no other game I play on it is graphically-intensive, and could greatly benefit from AA.
Overall, I would recommend looking at ATI or nVidia graphics for a laptop (e.g. AMD 690GM-based one with X1270 graphics) if you want to play games. Performance is similar to the X3100 (sometimes higher, sometimes lower), and the option to use AA would be great.
If you want gaming on a laptop, then you should really look into one with a dedicated graphic card. Even a low end dedicated graphic would be much better than an onboard. For example, my dell laptop with an ati x1400 plays WoW much better than my desktop with a GMA3100. That being said, if you don't mind low settings, than i guess the X3100 would be sufficient.
I have a Dell Vostro with a 1.8ghz C2D, 1.5 gig ram, Geforce 8400M and it plays Team Fortress 2 at mostly high and medium graphic settings around 30 fps with a few dips into 20's when things get really hectic.
From what I have read the x3100 is a minor improvement over GMA950 with better shader support. Wow isn't shader intensive so it doesn't see much if any of an improvement. Its still onboard video. From the videos and reviews, expect 20fps with low/medium settings. With my GMA 950 laptop (CeleronM) I find that I am cpu limited at the native res. My friend has a P4 mobile that fares a lot better (hovers closer to 35ish out of cities). Make sure you have at LEAST 1gb of ram (2 would be much much better) and don't skimp on the cpu.