Steven, I am a professional editor working on a pretty much spec'd out new Mac Pro, 20TB raided drives, 64GB ram, and the fastest dual graphics cards you can buy. Ive been editing digital film and broadcast television on non linear systems for 14+ years.
Premiere cannot handle my footage well - 2K, 4K. Even stuff shot 1080p gets very laggy on the timeline....in FCP once could jump around with ease, scrub fast through clips using JKL. Not Premiere CC 2014. You have to handle this with kid gloves. Tonight I am working with native C300 footage and it gets wonky on the timeline once you start scrubbing. It can do it, but not with butter ease as you would expect, as I experience with FCP, or AVID. And adding layers, color grading, etc. makes it even more volatile, and prone to it absolutely freezing up, crashing, (4 times tonight) I was sold on not having to transcode to Pro Res, but the software just doesn't feel that it is "there" yet. In my opinion.