i had the mx700 for about a year and half now. there's some considerations
1. The camera & led are not in the middle of the mouse like any corded mouse, this will lead to a problem if you're a high sens player (i.e using your wrist more often instead of your arm to move the mouse). If you aren't used to it, the cursor will go above (like a parabolic graphic) if you move the cursor to right, and go down if you move the cursor to left, instead of forming a straight line. This got me dizzy for the first time i used it to play CS, because the direction i move the mouse is not giving me the direction i want it to be, but you'll get used to it eventually (if you haven't so)
2. The mouse is very responsive for a cordless mouse, BUT it is not as sensitive as it's sibling mx500, because i already compared both and there's a slight delay in it.
3. If you are a low sens player you can't move this mouse too fast. For example if you want to move 25 cm as fast as your hand might able to do it, the mx700 will get 'dizzy' (i.e cursors moving in wrong direction), for comparison, mx500 can handle the test, no wrong cursor direction whatsoever. For a low sens player its a problem if u got someone surprise you form the back
4. after a year the left click gets somehow broken although not fully, i mean if i press with the same force (just a usual force) just like when it was new, it gives me double click (?), i must give more force to press in order to make the mouse's left click behaves correctly. for the record i browse a lot in a year and play a moderate amount of CS
but then again i believe my mx700 is the first batch of production, because i bought it on around february / january 2003, so maybe later batch is better. YMMV