I just recently replaced my G500 (had the same exact issue) with a 2013 Razer Deathadder and I like it. More comfortable than the G500 and the driver software is much better IMO.
Fewer overall buttons (left/right/middle click and two thumb buttons) and it lacks the free-spinning wheel mode (probably my most missed feature going away from the G500) but I rarely use lots of mouse buttons in games (even in MMOs I use mouse buttons as modifiers so I can have a single keyboard key bound to 2-3 actions easily accessible by holding a mouse button).
I do use a palm grip on my mouse, so comfort may change w/ a different grip. Another thing to be wary of, the Razer software uses a cloud-based profile system. It has no internal memory (that you can write to) so if you want all your settings on another computer you must install the software and log in to get them.
Other than that, I've really enjoyed it so far.