Well, I'm afraid it is all about the dpi...
Came home today with a MX700. Charged it all the way up, popped it into the USB port in place of my Boomslang, and loaded up UT CTF-Face to see how it does for sniping. Utterly morbid compared to the Boomslang. It just skipped all over the place, much like the Intellimouse Explorer I had before buying the Boomslang. All I did was just load up the max number of bots possible, set it on the easiest difficulty, and then let the other team's bots all come out. With the MX700 it was just impossible to clear the bots away in one sweep because it was impossible to get a bead on the head in one try. Swapped back in the Boomslang, and it was like a turkey shoot, just hopping from head to head and taking out a whole row of bots in one sweep. Make no mistake about it, the extra dpi's DO matter. It was just much easier to track with the Boomslang because it didn't have nearly as much pixel hopping as the MX700.
And speaking of ergonomics, I found it quite difficult to go into each weapon's 2nd shooting mode using the button under the wheel without easily knocking the wheel up one or down on the MX700. That got annoying real quick. Not a problem on the Boomslang, pressing the wheel button down does not spill over into the scrolling.
The MX700 goes right back to CompUSA tomorrow...and the refund goes to buying a spare Boomslang 2k or two!