Just went through the buying decision on this...
For the wife, ultimately upgraded her Feb 2011 17" to an Oct, added RAM, larger hard drive. She loves the screen, the performance is more than plenty. It's the anti-glare version, and to me it's the perfect notebook screen. I am a home user, dabble in A/V media, etc, but not a pro so I don't really perceive the finer points of color gamut or those critical pro-level mobile situations etc.
For me, I finally switched over from a 17" DTR Win 7 machine with a desktop processor--went from my trusty Hoss of a PC to a real laptop in the form of a non-Retina 15" 2.7 high-res/AG, which is awesome. The 15" high-res is clearly smaller in terms of desktop real estate, but it hasn't left me short in any practical way. I checked out the Retina, it looks cool and I think it might have all-told been same or cheaper than how I ultimately went, but at normal laptop viewing distance the Retina didn't add anything for me personally over the high-res (it was clearly better than the standard res for me). I know the supporting software is being improved and ML is coming out, etc etc, but I perceived that the GPU might be struggling to fully support it... like it's almost there and the next generation will be great. I love where Apple is going with integrating/fusing different sources onto the display, but I don't have anything happening that requires me to be on the leading edge yet. I also had an available SSD drive, so the non-Retina was good for me, loving it so far.
Two things struck me as key in my decision on Retina or not is that it's just a laptop display, and I separated that from the other computer parts. (1) if I need higher-res, larger display, I can connect to an external display which is 80-90% of my use anyway. Best of all worlds in my opinion. (2) I was tempted to hang back a generation and use a 17" and see what happens next year... but I also had situations with my Win 17" where I thought it would be much more convenient to have a 15" and that great macbook trackpad--the Jun 2012 cpu and gpu upgrades won me over.
So far so good, and we'll see how I really use this once the "new car smell" wears off; i.e. the tremendously increased convenience of the macbook may entice me to use it in a more mobile manner. Along with this, I think the pound less of weight of the Retina isn't a big step really (after my previous 11-lb wonder), but perhaps an iPad would really be right for an in-between role, we'll see.
Food for thought, I hope it helps others in their pre-purchase research... Cheers!