Used a Mac at home for 2 years now and love it. I did use them at Uni for 3/4 years so it was nothing new to me, I spent £1,000 making the best PC money can buy 4 years ago and had nothing but probems. Which was nothing new as PC's seem to always play up ... *Cough* Blue Screen of Death *Cough*
I am running all applications that I need with no problem.
But remember a 3GHz PC will not be as fast as a 2GHz Mac ... Infact nowhere near.
As a graphic designer I use a fairly powerful PC in work (something like 2.8GHz and 512Mb of Ram) and my Minimac at 1.66 Intel Duo with 512Mb Ram eats it alive.
My work PC is getting updated this week and the Mac will be updated soon to 1Gb Ram.
The only downfall was when I am doing ASP.net etc I need to use a PC
I found myself a PC on the Evo car forum for £50 and it's awesome for what I need ... albeit it still crashes.
Applications shouldn't prove a problem with the option of having Virtual PC or any other PC emulator.
I've convinced 2 people to convert and they all say they'd never go back and neither would I.
What Mac are you looking to get?