I went from a G5 to a G500 to a G700. I'm LOVING having wireless for the mouse, as the cord always gets stuck in something, or it drags across the mouse pad.
I love the G700, but I already had two mice with problems where one of the buttons wears out in less than 6 months. I thought about jumping ship to Razer, but I heard their mice also have that problem every now and then -- I'm guessing they use the same button manufacturer or manufacturing process. Another big reason why I haven't switched yet is because Logitech has incredible tech support. They will replace your hardware very quickly if you're having issues.
If anyone knows of a great XIM3 wireless mouse that's up there with the G700, please let me know