I've used the MX1000 for about a year now, and I switched to the G7 about a month ago. Here's my thoughts:
MX1000
Pros:
Long battery life - probably 20-30+ hours
More buttons than you'll ever need
Decent software / button programmability
Cons:
800 dpi - getting dated
Long charge time - mouse has to be docked while charging
Button placement - unless you have an EXTREMELY large hand, you'll probably find some of the buttons impractical
The pads started wearing out toward the end for me.
It only comes in a
blueish-green / black color.
G7
Pros:
2000 dpi - huge performance increase
Awesome gaming "feet" - they glide much smoother than any other mouse I've used
Comfortable design - I have a medium / large hand, and it never cramps
Swappable batters - no "Oh crap, my mouse is dead, now what?"
Decent software / excellent button programmability
Comes in
silver / teal and
black / black.
Cons:
Expensive
Very short battery life - I'd estimate about 10 hours or so
Fewer buttons than the MX1000
The dpi-selection feature was a huge marketing hitch. I have yet to find a use for it.
Overall, both are good mice. If I had to buy one again today, I'd probably get the G7. 2000 dpi has made a noticeable increase in my FPS performance, and even though the batteries die fast, there are two of them. One is charged long before the other dies. With the MX1000, I'd sometimes forget to put it on the charger and end up having to use my notebook mouse to get around.