I purchased the mid-2012 rMBP 15" base model (with dedicated GPU N650m) at launch. It's a wonderful computer and the screen is amazing, in fact I never thought I'd downgrade to a smaller screen in a laptop. So moving to last week, I picked up a late 2013 13" MBP mid-range specs. I still haven't decided if I will return and keep my 15" or stay with the 13". I wanted to try out the new MBP for several reasons, faster processors, read/write speeds on newer machines, have a lighter laptop, and a laptop with much improved battery life. I tried the 13" MBA but after using a retina display (also have a 5S and iPad Air) I can't stop unseeing the low resolution issues on the MBA display, also the viewing angles are terrible.
I like that the 13" has a faster processor but the best thing about it is the battery life which is 9-10 hours. The 15" model's battery life isn't as good. I think that's something to consider between the two models. If battery life is important to you consider you get much more out of the 13" model and you don't lose much. I don't do any content creation or video editing, so I feel the i5 processor is fine for me. I will say one thing about this two year old computer. Two years ago this was almost the top of the line mac laptop to have, and it's still very capable machine. I'm going to try and sell it on ebay for $1000 but I feel very guilty for doing so given that there is not that much difference in performance between the latest mid range MBP 13". In fact in terms of graphics the N650m blows away the IRIS and IRIS Pro graphics of the latest MBP models.