Another happy Logitech G500 user.
I'm not a gamer so I use the DPI buttons for copy and paste, the extra button between 'forward' and 'back' for search (i.e. highlight anything, anywhere, and click to search Google). This has saved me a hell of a lot of time. DPI buttons (you can have a profile that is automatically activated when using certain programs) are really handy in Photoshop and so on though.
I want to say that having a 3-year warranty is quite important for me, and a lot of Logitech products have this. I had a good Saitek mouse in the past but the clicker failed after about a year.
By the way, how have people found the battery on the Performance MX? It was bad for me, on two separate units, but reviews said it was good. I would choose a wireless G500 over a Performance MX by the way, but wirless would be really helpful for me.