It's a bit long, but this is a good read about the state of FCP by
Philip Hodgetts:
A very big reason people go w/FCP is because it can do a lot for very little money. If it was priced more in line with Avid Media Composer or Avid Adrenaline I'll bet dollars to doughnuts it wouldn't have become as popular. Apple's typical method of operation when it comes to the ProApps is buy existing software, rebrand it and drop the price dramatically. The most recent, and most radical example, is Apple Color. Apple took what was previously a $25,000 color grading application and tossed it into the Final Cut Suite at no extra charge.
ProRes has only be around since FCP 6 and is one of the few additional features that Apple can really hang its hat on. While Premiere doesn't have any first part codecs along the same lines as ProRes it is more flexible and open to third party codecs than FCP is. A very good, and very popular, 3rd party codec is CineForm.
Lethal