This mouse is nice-nice! I have a gen1 mouse out of warranty of course, but have repaired the two normal problems in it (battery charge - cheap wiring connectors in charging unit / soldered and now working great) - (Click & Hold - cheaper micro switches / cleaned and added mercury to contacts - DO NOT TRY THAT AT HOME UNLESS YOU KNOW WHAT YOU ARE DOING mercury is VERY dangerous & you need a microscope to do it). They fixed these problems in the Gen2 versions (green & silver).

This mouse is able to avoid game specific changes to the mouse so you can retain your pre-set, or profile specific mouse resolutions (Between 400 to 2000 DPI) not to mention the on the fly selectable settings on DPI for really accurate sniping at long range.

Battery life is good, and with the charger in high charge mode you can click out non-stop. The mouse only has 2 Bluetooth channels so running more than a couple of Bluetooth devices will cause problems - my MS Bluetooth mouse can interfere on reboot sometimes.
Dirt and dust do not seem to bother it, cat hair does however (dang cats! Heh) although not as bad as normal optical's.

I ran the tweak programs (not needed in most situations) to upgrade the mouse USB poll rate to 750 on my machine and it seems a touch more responsive and less prone to 'jerks' in most cases.

While I don't like a lot of Logitech's lower line stuff, their gaming stuff (from what I have seen) is top notch. If you cannot find this mouse, the G9 or MX Revolution is the same basic mouse.
I would give this mouse a 9.9 out of 10; Highly recommended for gamers.