I got the Performance MX for a Mac Pro, had it for a few weeks now. Regarding battery life, I have been disappointed. I think I've charged it three times already. I think it needs a charge more than once a week. I do use it 10 hrs a day and never turn it off. Perhaps the battery that shipped with my mouse isn't the best? Or maybe it's working harder on my black mouse pad (yeah, I dont need one but I like the traction feel of the fabric pad). I guess I'll need to experiment more. I don't see others complaining about the battery life. My original logitech MouseMan lasted months on one set of batteries (2) - so the difference is huge.
The good news is the battery is a (single) standard AA NiMH, so replacing it is dead easy. It can be charged via the included USB cable while using it, so that makes it simple too. My only complaint here is that Logitech decided to use a rare female connector on the mouse. The connector is very similar to what you see on most digital cameras, but a bit smaller. It they had used the same connector, I would just use the same USB cable for my camera and save on the clutter.
My only other complaint is the scroll-wheel. It detects sideward presses, which sounds cool. But it comes at a cost of making the scroll-wheel clicks flaky. You click the scroll-wheel and nothing happens, because you didn't press *exactly* straight down .. it is really picky about that. Even if you get the click, if you were leaning the button one way nothing happens! It's annoying. I had to configure the scroll-wheel click and the right press both to dashboard and I've learned to just press to the right. Now it works about 80% of the time. (I have the left sideway press to show/hide the dock, which is nifty). The free-wheeling scroll-wheel I think is useless. I would rather have another button up there than the button that lets you enable/disable the ratchet.
Everything else rocks about this mouse. The usb receiver is tiny and fits nicely on the new mac keyboard that ships with the mac pro. The logitech drivers work really well on Snow Leopard. I was surprised. You can setup the 9 (yes - 9) buttons to do whatever the hell you want, including different settings for different apps.
A tip from me -- if you want to bring up expose/spaces/dashboard using the mouse ... do it this way... let's say you want the thumb button to bring up expose. You can set this function in the Logitech Control Center directly, but I don't do it that way. The reason is that the button won't be able to do any other useful things .... like holding down command and thumb-click to do something else (like application windows expose). So what you do is set the Thumb button with the action to "Advanced click" .. and in that, the Click Type to "Click" and Button number whatever you like (say 7). Now the thumb button is "mouse button 7" to the rest of software on your mac. So you go over to Expose settings and set up shortcuts to use mouse button 7, and command-mouse-button-7 for applications-only-expose... etc. I also set my zoom button to Go Back in the browsers - via Keystroke of Command-[. And I set it to other things in other apps. Pretty darn sweet.
