I CAD for a living, so wireless performance is a high priority, and a higher price is not an issue. The only decent options are the gaming companies. As far as I've been able to find, no one has an ergonomic wireless left handed mouse, not even Razer, but if they do, I'd sure try it. Logitech wireless mice don't cut it. I was using them for years before I got a Sensei, and I think I've tried one of every model.

I'm using this one. It's symmetrical including the buttons, so it's ambidextrous, not ergonomic, but even after a 12 hour day, it's still comfortable. There's no lag like the Logitech models had, and I can adjust the tracking to exactly the way I like to move the mouse.