I got the logitech g5 today.
The lack of mac drivers is a piss-me-off. Without the drivers, all you can do is left/right click, scroll up and down and change the dpi via dedicated buttons. You can't customize anything, scroll left or right or re-assign the many buttons.
Installing USB Overdrive solves 99% of problems. The dedicated DPI buttons stop controlling DPI, but the software allows you to assign all the buttons (also as keystrokes) and change the DPI via software. You can also have unique profiles for different programs, so if your program allows dpi adjustment via keystrokes, problem solved. Warning: do not install logitech drivers found on Apple's website. They'll mess up overdrive.
Personal opinion:
I don't really have any complaints. I suppose on-the-fly DPI adjustment could be cool if you're switching constantly from photoshop, gaming and general use (and you're anal-retentive). I don't play games and find them much more useful as cut and paste. I like the single thumb button (im a simple creature, two gets me confused), so the G5 button setup is good for me.
Mouse works well for general computer use and performed fine with photoshop. The DPI adjustment might help delicate tasks, but really not a big deal. If you are anal-retentive about DPI, prefer two thumb buttons and/or left-handed, the G5 may not be for you.
Overall, im happy with the purchase. I am using it on a wood desk, without skipping. It "feels" well-built, comfortable and not cheap in your hand. Its ergonomic for righties, without being TOO ergonomic. The details is what sets this mouse apart. The weights are not necessary, but a cool gimmick nonetheless. I'll admit it, I wasted 5 minutes getting it JUST right! The braided cord is also nice touch. I hate apple mice and used only microsoft in the past. For now? I'll stick with the logitech.