NOTE: This mouse originally had extreme lag with the mouse pointer, this has been fixed in a firmware update so do not be put off by reviews saying as such.
This mouse is very comfortable and feels like it is made of quality parts. With that said, it is definitely more for palm grips than claw grips like myself.
The textured sides took a bit of getting used to but I don't really take any notice of it anymore.
By far the strongest part of this mouse is the Logitech Gaming Software that Logitech uses for all of it's products. There are so many features and the built in macroing with both a GUI and LUA scripting makes the possibilities endless.
One of the only problems I really have with it is that the 3 mouse buttons on the thumb can be a little hard to tell apart in the thick of action, I'll occasionally find myself pressing the wrong one.