I've been using the Kensington Orbit (optical, and before that the old non-optical) for years and I like it a lot, I find it very comfortable.
I use it for everything, including games, without any problems. I'm not a hard-core gamer, but I spend my fair share of hours gaming and while my skills are probably only mediocre at best, I don't have any difficulty gaming on it.
My biggest complaint would be the lack of a middle button (or any other extra buttons, for that matter). Lack of a scroll wheel is slightly inconvenient, but it doesn't bother me too much - most of the scrolling I do is in firefox, and I have an addon called grab and drag that covers that.
I've heard good things about the Expert and Slimblade, but I haven't tried either one. I wish there was local storefront where I could try one out, but I've never been able to find one.
PigLick
