[Stealth-]

I do both regularly. They are different hands and the different movements actually become very different feeling. When my right hand is on the mouse, WASD feels natural. Otherwise, I naturally hold my left hand near the ESC key and my right hand over HJKL.

Because it's the home row, it also feels more natural when you are getting ready to type. The mental separation between "gaming" and "typing" is not hard to get a hold of really quick. Give it a try! I guarantee you'll be completely used to it within a week.

Also, keep in mind all of these keys can be remapped in Vim anyways :)

[McPants]

It seems like that person I have been waiting for to create that mapping is me!