I have heard the Beats Pro with my iPhone 4 playing lossless audio files and at the Best Buy display. The sound of the Best Buy display sucks. The phones sound better than that. I actually like the Beat Pros a lot. I am still suppressing an urge to get a pair. They are funnest pair of phones I have heard on my iPhone without an amp. Extremely dynamic, punchy, very wide and deep soundstage, and really good bass.
I wonder if I can find a better pair of phones that can be driven this good by an iPhone?