I was really surprised too until I looked up the 520M. I thought the 520M was a 420M with a clock bump, not unlike what the 525M is to the 425M. The 420M is not far from the 5650M (about 10% slower) so it wouldn't make sense for a speed bump to not bring it closer, if not match the 5650M.
Except that the 520M is more like a 415M with a clock bump. The 415M only has half the number of shaders compared to the 420M. Driver advantage aside, is probably slower than Intel's Sandy Bridge. Apparently, the 520M is only meant to compete with Sandy Bridge, and manage to be a bit faster (and again with better game compatibility). So the game has stepped up enough that the best IGP/“fGPU” can take on nVidia's worst.
Not to take away AMD's accomplishment, the Llano is ahead of Sandy Bridge in terms of GPU performance, and ACF will be very interesting once they get it to work properly (I am optimist in the same way that I was about SLI/CF in the early days when lots of people questioned if they would ever be viable). But it's fair to say that Intel is not left completely in the dust in such a way that it's hard to see them catch up with their next offering. None of the benchmark in this review shows a Sandy Bridge laptop (edit: actually, I am being silly - this MSI laptop *is* a Sandy Bridge - it would've been nice to seen the Intel GPU benchmarked too though). You can see here the difference between the the Llano, SandyBridge and the old Intel IGP (so far behind it's laughable):
http://www.anandtech.com/show/4444/amd-llano-notebook-review-a-series-fusion-apu-a8-3500m/10