In my experience, a laptop is ****ty for gaming. For any moderate or faster paced game, being able to quickly and accurately manipulate controls is a major necessity. That being said, I can't even stand playing Diablo II with a low level character on my laptop unless I plug in a USB mouse and set myself up at a desk (or makeshift desk). The keyboard presents less of a problem, since mine is full size minus a numpad, but I haven't tried it in an FPS where the keyboard would be more important.
If you really want a laptop for gaming, I recomend that you have a desk area set up that you can game at. I'm assuming you really want to be able to take your computer with you to places, that is obviously the only thing that would make getting a laptop worth it. Don't expect to sit in the LazyBoy and do some good gaming (unless you get real creative