I use Win7 Pro on my Macs with Parallels Desktop 8 and
it functions quite well for engineering apps. As far as Windows8,
as far as I'm concerned, I'll be using 7 until I can't use any my Windows
software due to updates requiring Win 8. From a productivity standpoint,
Windows 8 is a joke. Even with most all my engineering apps, they
work well in virtualization with no need to go Bootcamp.
As far as getting Win7, Newegg still has both full retail versions of
Windows7and OEM versions. They also have OEM Windows 8 as
well (not upgrade). The difference between OEM and full retail versions
is that there is no Microsoft support available for the OEM versions.
The assuption being that if you are building PC's, you don't need Microsoft's
help. The other difference is that you need to select whether you want 32
or 64 bit in OEM, where full retail contains both.