The MX700 was the most comfortable it lasted about 6 years then crapped out. Now I use a MX Revo and I found I had to move the USB dongle closer to the mouse. When plugged into the back of the computer (which sits under my desk) it would lag. My keyboard has usb connections so I plugged the dongle into it and I haven't had any issues since.
Same here... fortunately my monitor has a USB connection in it. As soon as I moved the USB dongle for my MX Revo out from under the desk all lagginess went away.