I wouldn't be so concerned with the processors.According to this report and to the report from Apple insider, the performance is really disapointing. These old games should really run very fast on such a sophisticated OS and although the tested GPU was not dedicated it is faster than the fastest dedictaed GPUs from when these games were released years ago. Additionally I used Geekbench to compare the performance of Windows to the performance of OSX (on my MacBook Pro) and OSX was always significantly faster. So a properly coded OSX title should always yield higher framerates then the same Windows coded title on the same hardware under Windows. Lets hope the performance will at least double towards the end of the beta!
In addition OS X gets some disturbingly high floating point scores in Geekbench. It can't be replicated on the same hardware under Windows.