I have been doing all of my work from a maxed out, late '09, iMac. It is well past it's prime and is barely getting by with the video work I am currently doing. For example, an 18 minute video with full color grading, sharpening, adjustment layers, and some skin retouching, just took it about 14 hours to export. Yes you heard correctly. Even worse, the black and white music video I did for the lovely Tyler Guthrie took about 30 hours to export. I am about to bite the bullet, pull the rip cord, or whatever metaphor you choose, and buy myself a brand spankin' new iMac. I knew very little about computers when I bought my current machine.
I may do more of a review of it after I have working with it for a while, so stay tuned!