Hey,
I´ve been using a 17" MBP from 2009 (that I still have). Bought/switched to retina this summer.
First of all: the screen is much, much better generally speaking.
I´ll also submit that the machine overall feels better, both design wise and performance wise. Fair enough, it being the next step in the Apple evolution.
Obviously size and weight are huge improvements coming from a 17".
However, there are a lot of smaller features that I really appreciate. Keyboard, keyboard illumination, tightness of lid, fan construction, start button - everything is slightly better built. Love the little tilt they gave the hollowed out lid opening space in front of the track pad (for lack of better name).
Screen: I use a 1680x1050 resolution (the best fit for my daily use of Pages).
Everything looks and feel better than the 17" screen. Coming from glossy, the improvement is
radical. You might be a tad better off with the matte when it comes to reflection on the glass, I don´t know. My point is: reflection is not a big issue anymore, as it definately was with the 17" glossy.
Looking back at the 17" screen, it now comes out as too bright, and it almost has a "hazy" feel to it compared to the retina. My personal opinion is that the retina feature is a much bigger improvement that anyone can understand before actually using it over some time. I would, could and should never go back.
Performance: The retina does not feel as responsive and snappy as my 17" 2.93Mhz 4 GB ram and SSD. The retina can sometimes lag after hibernation. Sometimes it lags when using several apps at the same time (example: iTunes music can hiccup whilst surfing the net). And I did notice some screen flickering before the latest update. I think that means it´s an OS thing and not a hardware thing. The point is: I am not experiencing a faster machine here, and it almost feel like a drawback. Another thing is the battery, which is not yealding me more time, but approx the same as before. All in all the retina MBP performance feels quite solid, and I have a sense the machine is going to serve me well in the years to come.
Design/usage: Aside from the size and weight, the biggest improvement is the "tightness" of the design. It simply looks and feels much better. You are truly immersed in your content. Everything from the glass track pad to the keyboard is more than satisfying.
Conclusion: For me, the move has been good, if not overwhelmingly so. The retina screen is the true gem, and I have absolutely no regrets coming from a 17" screen. The performance of the machine, however, is just a little disappointing. But then all that might change with the next OS update ...

P