I used to have an MX700 and upgraded to a G7. The design is more or less the same so it feels great to use. It doesn't have a forward button but I don't really care about that. The DPI setting buttons are great for FPS games. The battery life is a lot shorter, but you can easily swap to the other battery without losing the connection.
I also got an MX 3000 keyboard/mouse set which comes with the mx600 mouse. I don't like it too much. The back of the mouse slopes more so there isn't as much support for the base of my palm and thumb. The bottom, rear of the mouse doesn't have mouse skates or mouse feet so the entire mouse will tip backwards slightly when I pull back.
If you're considering an MX3000, don't get one if you're a quick typist. I hover between 60 to 80 wpm when I type casually and there is a very noticeable lag for me on the keyboard. The problem gets worse when I code or transcribe text because I type closer to 100 wpm when I'm doing that.