I just built a desktop with a gtx 570. I play on ultra settings but framerates are only 20-30 in Sanctum and 30-40+ in the rest of the world. Just a data point for you to compare to, I'm not sure how the mobile cards compare to desktop cards.
Actually I have a couple more data points on my 2 older laptops.
Gateway gaming laptop, I *think* has a 9600m graphics card and it could hardly play at all on low-rendering mode.
Asus G72 laptop with a 260m graphics card could also only play on low-rendering mode but played smooth.
I don't have any other specifics on the laptops since I'm at work, but I'm pretty sure those are the graphics cards and I couldn't get out of low-rendering mode on either.