This was nice, pretty much straight to the point. At Dropbox we've noticed disproportionately more Mac/Linux users (relative to the "worldwide norm" or whatever that means, which is pretty standard). More importantly, we've definitely noticed disproportionately more vocal Mac/Linux users. We started as Mac and Windows but "investing" in a Linux (ok, Ubuntu/Nautilus to be specific, but it tends to work in most distributions and can work without Nautilus) client has certainly been worthwhile.