There is no other reason to have it, in this house - everything else I do with my Mac, I can do equally well if not better with my Linux workstation.
Its just that its almost impossible to work on iOS without XCode, and so far the XCode VM I set up for the purpose isn't as performant as my MBP.
I'd love to ditch the MBP, though, and just have a plain ol' Linux workstation. I don't see anything terribly unique about OSX in comparison.
