I’m an engineer. I actually spend most of my time not in Windows, but Linux. So let me be that official voice that you can have things not suck on a PC without Windows...Ubuntu is very user friendly.
That said, it’s not as friendly as a Mac. But what interests me in Mac (the BSD nature), is unlikely to mean anything to you. If money were no object, I’d buy Macs. But I cringe at the idea of spending more than 8 or 9 hundred dollars on a computer. If this is not an issue for you, go for it. But then again, I have hacked MacOS on to my $900 PC that’s faster than the $2000+ Mac Pro ;)
I'm curious... exactly what processor are you using in your $900 machine that is the equivalent of the 8 core 2.8GHz Intel Xeon processors in the Mac Pro?