AnandTech: AMD's Phenom II X4 955 Black Edition
Here is an in-depth review of the 955. It is overall beat in pretty much everything by a stock i7 920. There are a few games where it pulls ever so slightly ahead of the 920 but a very minor overclock to 3.2GHz on the 920 (which is very easy and would put it at the same freq. as the 955) would put it back in front I'm sure.
They also overclocked both and the 955 proved to not be a very good overclocker. The highest they got it was 3.9 (a 22% OC) on 1.425v while they got their 920 to 4.0 (a 50% OC) on 1.35v.
In all of the productivity tests and such, the 920 wiped the floor with the 955. This article still makes it pretty clear what the better processor is.