My main computer is a MacPro late 2007 which is still okay for me.
However some months ago I decided to just "try" a PC (my first PC ever !!) and bought a very powerful custom configured i7 with everything we could throw into it. 128GB SSD, 1TB drive, 16GB ram, USB3, eSATA, BluRay burner, best and most silent Coolermaster cabinet, best power supply, top notch 580 graphics card, front mounted "dock" for connecting a hard drive, front mounted card reader, best keyboard and mouse, and of course Win7 pro 64 bit.
I have the complete CS6 production package on this PC and CaptureOne Pro 6. Startup time from when I push the power button until I can login to Windows is 10 seconds ! After Effects rendering is just blowing through the machine.
I am still a mac guy at heart, but I have to say that I am amazed of how much workstation I got for my money. (I paid apx. USD 1800,-)
Except for the Command / Control key use different from what I'm used to, when Lightroom 4 or any other program is open, there is not much different. It does the job and connecting to the other macs on my network is no problem.
BUT... it's not a mac!
No matter if Apple upgrade the MacPro line, I like the idea of having ONE very powerful MacBook Pro laptop with an external apple monitor and then use this as the main computer in the future. The less cabels, monitors, speakers etc. the better.