The wild, nearly out of control growth of smartphones and tablets has computer makers rethinking what goes into their desktop operating systems, CNET reports. Notably, Microsoft and Apple are taking significant measures to address the success of mobile on their next desktop operating systems by making them closer to their smaller counterparts. So how do these early “fusion” OSes hold up? Let’s start with Apple’s new version of OS X, which made its debut earlier today in the form of a preview to developers. Apple’s calling it Mountain Lion, and as the name would suggest, it’s not a stern-to-stem overhaul, as much as some refining and additions to what the company did with Lion last year…