Con: *NIX software isn't as easy to install. I mean there's stuff like brew and ports, but it's just not the same. You have to sit there and compile and then oops you have a problem you need to go fix. For instance, postgres9.0 on ports has a bug where you have to specify the hostname, so you're doing psql -h localhost just to bind to the local database. I hear brew is better but there's an opportunity cost to switching and making sure everything installs.
No hibernate option, not that it always works in Linux.
Pro: No Unity interface :). I jest, but some people don't like the UI and that could be a pro for you.
Mac App store is definitely a plus, but apparently Ubuntu has one too.
You can use Xcode and be able to play in the iOS sandbox.