I already have one MX500 and went for one more on this deal instead of the MX700 because mouse cords has never bothered me. I think the mouse is more confined by the mouse pad rather than the cord, and I didn't want to have to remember to put the mouse in the charger everynight.
Btw, this is a great mouse, every bit as precise as any ball-mouse I ever used, the "back" button is the best creation ever on a mouse, and those "cruise up, cruise down" functions are useless (basically duplicating the wheel functions) but when remapped to "close window" and minimise window" -- they aren't too bad.