Apple's recent lineup of laptops and iMacs are fairly impressive and offer a lot of performance for the price. I don't know that I've ever seen a better time to get a new computer.
Look at the 2011 MacBook Pro 17" 2.30GHz with 8GB of RAM -- it is damn near as fast as the Mac Pro 6-core tower with 24GB of RAM for Photoshop CS5:
Kick it up another couple of speed notches with the Mercury Extreme Pro 6G SSD and get over 500 MB/s read and write speeds, in a portable computer!
Is the new iMac 27" the very best bang for the buck on the market? It certainly looks that way for the indie or small business filmmaker. But I am confident a LOT of commercial photographers will choose this computer as well. Why would you want/need a more expensive MacPro (unless you had custom cards you needed to install for custom drives/video or we find out the screen isn't up to snuff for some reason)? Heck, just look at what a 27" Cinema Display costs on its own and the new iMac is one sweet machine.