Well for software development the only problem with Windows is that it isn't unix and a lot of the web dev world lives on unix. In my experience Windows 7 is much more stable than for example Yosemite, though I would really prefer to use some linux distro.

Osx just seems to have a lot of problems with very basic stuff like beach balling various system dialogs, failing with external displays etc.

The hardware is nice, especially the trackpads are way better than the stuff for example Lenovo puts out. Though I have to admit that I really don't like aluminium as laptop material.