I don't know if this is expected for these GPUs, but from talks on #intel-gfx, it does seem like there is something out of the ordinary, and I was told to file a bug. When playing Portal under wine on my i5 M520 with its on-die GPU on a Thinkpad T410, the original Portal drops to a low framerate whenever a Portal is looked through. There is generally a low framerate in Portal 2, which does indeed get lower still when a Portal is looked through. It's a very dramatic difference; without a Portal on the screen, the game usually runs at an acceptable framerate; with a Portal anywhere on the screen, it slows to around 5-10fps. I've disabled GLSL in wine due to another bug (which I'm about to file), but even with it enabled, the framerate difference is about the same. Kernel 3.6.11-gentoo. A longer discussion that I had about the issue has been previously pastebin'd here: http://pastebin.com/cckwXQVC (in case I missed anything from this description).
Sorry no one ever investigated your bug.
Please test a new version of Mesa (12 or 13) and mark as REOPENED
if you can reproduce and RESOLVED/* if you cannot reproduce. Lots of performance improvements have gone into Mesa and the i965 driver since 9.0.
You should also try setting INTEL_DEBUG=perf and see if it tells us anything interesting.
This Mesa bug has been in the "NEEDINFO" status for over 60 days. I am closing this bug based on lack of response but feel free to reopen if resolution is still needed. Please ensure you're supplying the correct information as requested.