- Focus follows mouse without auto-raise - Instant switching between virtual desktops (not possible to disable the animation in OSX last time I checked) - Instantly open a new terminal window with intelligent window placement in the currently active virtual desktop.
Since these turned out to be a hassle in OSX, I've just gradually stopped using them, and resorder to a single desktop paradigm with more mouse clicking for navigation. All in all I feel like I'm working slower in OSX than in Linux.
However, the major problem with Linux is the looks and a host of small nice details that OSX just gets right. Instant search in Spotlight including Mail, I've grown accustomed to the Mail app (Thunderbird search is ridiculous compared to Mail.app, for instance), Time Machine, and a few other apps like 1Password.
If I could get a virtualization scheme where I could have one desktop with OSX and 3-4 desktops of Linux, that would be ideal. But I don't think that's possible with Parallels or VMware, and I'm not sure how well OSX would run virtualized under Linux.