No, it doesn't slow it down at all, but it's just a waste of money to have the power and never use it.
I equipped my 8800m gtx with a 2.1GHz t8300.
Some say the more power, the better, it'll take you farther down the road, but IMO, you should look for a notebook with a not-so-beefy processor, and possibly save yourself some cash.
However, the 8600 will do fine for those games.
The notebook is a great choice.