I'd have to say, in gaming, clockspeed doesn't mean shit, as said before. I recently got a notebook. Allows me to play CS:Source, (marginally but yes). I'd have to say, look for a graphics card over the processor speed. A good graphics chip will beast over anything integrated at higher clock speeds. Case in point, my notebook is a HP Pavilion z5000 line with a Turion 64 ML-40 (2.2 GHz) with 1GB of RAM and a Radeon Mobilitiy Xpress 200 chip (ala, ATI's line of integrated chips). CS Source runs about 25-45 frames per second on a regular basis. If that gives you a rough estimate, there ya go. But yes, a 1.8GHz computer using a GeForce Go 6600 or something would kick my notebook's ass in gaming performance.

If you wanted to know, the battery life is roughly 1.5 Hours running at 2.2GHz the whole time. I haven't checked it at 800MHz. If you didn't know, AMD (and I believe Intel now) has developed new technology that reduces clock speed in order to save battery when the speed is not needed.

Intel has been using the speed reducing technology in laptops for a while through the Pentium M line. I think the Intel version goes down to 600mhz however.