I have an 27" iMac from early 2008 that has a 2.4 GHz Intel Core 2 Duo, 4 GB SDRAM and an ATI Radeon HD2600 Pro with 256 VRAM. It is clearly NOT approved for use with FCP X according to the Apple website. Never one to listen too closely to the rules I downloaded it anyway to give it a spin. Thus far, on my family video clips, and HD camcorder videos, it works passibly well, with some stuttering during playback. But it is not too severe and most other functions seem to be working well. I've done a few test projects that did not seem to hang up. Overall it is quite workable. You don't want to do anything too serious with a non-approved Mac, but if you have modest needs and are looking to get some experience with FCP X, you don't have to spring for that new Mac just yet. But if you are a professional...well, you don't need me to tell you what to do.