Sadly, the best Ergo device around, the Fingerworks touchboards, are no longer being produced, but that's what I use for EVERYTHING, gaming, work, etc.
They combined the mousing and typing surface into a single split area, and added gestures for common tasks for good measure. They really had to be used to be believed.
I just grabbed the demo for the a relatively new fps I've been hearing my pc-gamer friends complaining about requirements for (Prey), installed it under crossover beta 2, and played through the first 20 minutes on my poor 1st gen intel mini, who's only upgrade is going to 1gb of memory. (Oh, The sacrifices we make for science)
I had it use the default graphics settings across the board, and it was smooth and quite pretty. Noteworthy, this is an _entirely_ unsupported game for crossover and it works fine. This is a pure DirectX 9 game, btw.
Now, this is an entirely subjective test, no FPS recorded and no testing under Boot Camp (I won't sully my mac with a windows install) to compare, the test was mainly if an off the site/shelf current game would be playable, and if others go as nicely as this did, we're in for better days.
There is another answer to this question.
Crossover Office by Codeweavers (here: Codeweavers.com) offers abstraction for much of DirectX, and is only getting better. You'll get speed on par with native built Mac games, without 1. paying for a Windows license 2. Having to dedicate the space to a whole windows install and dealing with the vulnerabilities it introduces or 3. Having to reboot.
How Many People Actually Use Ergonomic Keyboards?
AAM: Getting Parallels to Run Games
AAM: Getting Parallels to Run Games