2 years ago, while I still had just a Macbook Air, I built a gaming PC, but choose all the hardware from the tonymacx86 guide so I could use it also for iOS development.
Last year I bought a Broadwell rMBP and relegated the Gaming PC to just gaming.
Imho, too much work to mantain it updated and properly working. If I was still in high school, I could live with all the cons, but as a working freelancer, I won't.