Depends. when playing games, do you often pick up your mouse and set it back down? in FPS, i have low sensitivity and to make a big turn, i swing the mouse right, pick it up, recenter it on my mousepad and continue the swing to the right.
if you do things like that, the MX1000 does have a delay/lag. after the mouse sense its been picked up, it'll shut the laser off to save battery power. once you set it back down, it takes about half a second for it to register that it has surface contact and turn the laser back on. that is the only flaw of the mx1000 and is very minor 90% of the people, the execption being players like myself.
if you do pick your mouse up often, i'd say got with the mx510.
that said, if you want wireless, look at mx700. it performs flawlessly and compares in every way to the mx510. i own mx700 (almost 2 years now) and i owned a mx1000 (returned after realizing the pickup-setdown delay) and used the mx510. i personly use mx700, but i did prefer the mx1000 and once they fix the laser turn on, i'll be buying one.
for gaming wireless, the mx700 works great (not sure about the newer mx900 bluetooth). the wireless feature does not contibute any lag. period.
brandon