I'm about to make this switch myself. 17" 1920x1200 to the Retina 15".
I used one in store and opened up a bunch of windows and sized them to how I'd have them at home and I found it cramped. This was at the default retina resolution. Then I set it to the higher 1920x1200 equivalent and it felt usable the things on the screen weren't too small for me and I was at the same distance I am at home on my 17" MBP.
I'd love a new 17" in Retina form with a 4K panel. But I'm willing to make the sacrifice and go with the 15" model for Haswell, 802.11ac, PCIe SSD, huge amounts of RAM etc
I don't blame some of you for not doing it though this is a very personal choice and I'm making a sacrifice and I'm not happy that I have to do it, but it is what it is.
Maybe you could grab a used or refurbed 2011 17" to see if that can get you through a couple more years.