Didn't see this posted in the first couple pages, but some good news for Mac users who have Logitech peripherals. The company has finally gotten off its collective rear end and released some proper drivers/software for OS X. I have an MX 518 that dates back to the first MacBook Pro I bought in late 2007. It's always required the use of Steermouse in order to get the tracking and buttons set up. Not any more. Logitech's software is surprisingly well integrated, with profile, button mapping, and macro support, even for a mouse as old as the MX 518. I've found it far easier to work with than the software from Razer (Synapse 2.0 and otherwise) or Cyborg (R.A.T. series). No crashes or major problems so far, and all the game profiles I've created (mostly Steam titles) have worked flawlessly. Download the software from here.