I have had my 27" iMac, 1tb fusion drive, 32gb ram, i7 quad core 3.4 ghz chip with 3.9ghz turbo boost and 2gig graphics card for two weeks but have yet to see any magic in it.
The screen is naturally more saturated (not always a good thing) and not as crisp as my pro photo 17" (brain fade on the way home, cannot remember the make)
Further, having learned all the short cuts for my old PC the iMac is not any easier to use. Yup it certainly is faster in processing power but that is it.
I am not regretting the change (I need the process speed for editing HD video), other than for the £ 1,200 I have had to spend on new software (CS6 etc etc) and two keyboards / mouse and magic pad (not sure what I prefer ATM) but not seeing the Apple magic I was promised.
If I was starting out with a new computer, the iMac is perhaps more intuitive, but as a seasoned computer user, hmm, not convinced it is a great leap forward.