1. When I close the macbook, then later open it, I am confident that resuming from a sleep state will just work. No other laptop ever (including modern linuxes and modern windows) has given me that confidence. Since I move my laptop around a lot, this is a vital feature for me.
2. Awesome simple networking. As in, who needs the full power of iproute2 on a laptop very often? VPN, wireless, connection sharing, etc just work right and powerfully enough that I never have to think about it. But I have a full suite of tools for liberating Internet connectivity at conventions that was not to hard to port from linux.
3. Good support for presentations. I can plug in a monitor and just go, presentations are a breeze. Unless things have changed in the last few months, linux still just doesn't play nice with this.
Now, Mac isn't perfect: things I still miss from linux land:
* Total keyboard control over window placement. Seriously, this is something that Mac people don't seem to get.
* Apt (ports, fink, and homebrew are attempts at this, but none very good and have poorly maintained repos)
* Highlight-to-copy mouse semantics (Now the counter argument is in the mac everything copy/pastes the same where as on a linux system there can be couple competing clipboards glares at kde.. this is of course a strawman the semantics are nice and have nothing to do with n clipboards).
HTH