I'm not a 'Pro' user, but that doesn't mean I don't appreciate a nice computer. I don't think of the 17" as non-portable, but I wouldn't want to carry it everyday in a shoulder bag or backpack either unless I really needed that big screen.
What I do like about the 17" is its generous screen size for open windows with a reasonable view size-wise of contents, sharp and clear non-glare version, and for me its moving around the house (important for me) and an occasional trip in the car where its again set-up on a desktop. A smaller laptop screen is a compromise in my thinking.
I'm now on my 3rd 17" having decided that if Apple has discontinued them it was a good idea to get one of the lastest/greatest quad 2.5ghz version available (my 2010 2.66ghz was going fine, but this is an upgrade) at the Apple refurbished shore while they were still available. BTW; good price, looks new, I can get 3-year AppleCare, and unlike a newly introduced computer, all the kinks have been worked out, it just 'works.'
I'll add 16gb of RAM and a SSD drive and move the HD over to the optical drive. Nice that it has Thunderbold AND the legacy ports for external drives I have on hand, plus the card port for other things (an internal SD card reader
). Should keep me going for a few years till Apple again offers [I hope] a new retina !7".