I think I'll probably expand on this post for a blog entry later on, but I definitely need to weigh in on this subject. I'm a lefty that's tried for a long while to switch over, most recently having tried with a right-handed Logitech G500 mouse with many of the gaming bells and whistles. I spent about four months on it, and never could get my head in the right place for it. As a lefty, a whole host of things are more difficult than they're intended to be.
I spend a lot of my time gaming, usually on a PC. Console controls don't bother me with the left-right difference, but mousing is a real hassle a lot of the time. In the OS, I'm fine and can use a mouse in either hand, but in games - forget it. And it's only partially due to the mouse itself. A bigger contributor to my problems has been the need to use the arrow keys and home/end cluster for most gaming controls. I've gotten quite used to using that area of a standard keyboard layout for binding my keys, and my muscle memory is deeply ingrained for both hands.
Unfortunately, default keymaps are designed for right-handers, which means a lefty like me has to go through and rebind 2/3rds of the keys in a game to get to the point of having a functional experience. More recent, or more complex games are sometimes impossible to master just due to running out of places to put binds that your fingers can actually reach. Games where you can't rebind anything... well, those games don't get played.
My four month attempt to switch mousing hands pretty much ended with me being pissed off after four months of getting my ass handed to me in everything I played. I was constantly apologizing to teammates for shitty performance in Borderlands, taking far longer than anyone else to set up for an assault, and faster paced games like Team Fortress 2? Forget it. I spent a lot of time as an Engineer whacking a sentry with a wrench so it could do all the work.
I've tried the add-on keyboard controllers, the Logitech G13, the Belkin "SpeedPads", and a dozen mice over the last few years. Nothing seems able to shake my muscle memory out of the habits I've had with gaming since the Doom era when all you needed was weapon selection, movement and a fire button. The Logitech G13 game closest, but with its design quite heavily aimed at being used with a left hand due to a left-thumb positioned cluster of controls half of it is useless to me, and what's left doesn't feel quite _right_.
And even now that I'm sticking with a left-hand mouse/arrow keys keyboard configuration, I find myself still quite limited in options and controls. My mousing style is best described as a "fingertip" one, which works well with certain kinds of mouse design. With my keyboard needs, many of the current "ergonomic" models are simply useless.
At this point, the best companies I have to work with are Razer and Logitech. Razer may have a few dogs on the market, but they also have a capable midrange gaming mouse in the DeathAdder that comes in a lefty ergonomic design. Logitech may not be as nice to lefties with regards to mice, but the G-series keyboards haven't screwed with the fundamental 104 key layout. What those of us who can't adapt have been left with, is a pretty weak number of choices.
I have to give crazy amounts of credit to Razer, however. For a company whose products I once shot the hell out of in protest of a poor warranty situation - which they resolved, publicly and thoroughly - they really did step up. And in the case of the left-handed mouse, they claimed on launch that the left-handed DeathAdder may even be a money-loser but they still felt it was something important to do. Now, if only they'll step up the left-hand option to something like the Lachesis or Mamba.