I changed over from a MBP to a Dell M6600 laptop for CS 5.5 last fall and it works great with a M3000 cuda card. I edit EX and AVCHD footage and it plays in real time with three layers with effects. Have not tried four layers yet. I highly recommend a PC with the best cuda card you can get.
ronpesteshdvideo.com
Apple Certified Master Pro FCS 2
Sony EX-3
MacBook Pro
Dell M6600
Adobe CS6 Production Premium