I had a 1200RT for the best part of 18 months, great bike, very comfortable, superb screen which is particularly good if you ride a lot in the wet, handled far better than a bike that size should, with topbox and panniers there's few bikes with a greater luggage capacity. If these aspects do it for you then get it, don't allow other people to put you off 'cos it's got an older rider image.
But...
(Please consider that I may be biased for the next bit as I'm still in my honeymoon period with my recently acquired R1100S)
The RT is not sporty, and particularly if loaded is no where near as much fun to ride as the S. Whilst the fairing offers great protection from the front I found that it sent a draft into my lower back which became unpleasant on a long run particularly on a cold day. The heated grips were crap, setting one was barely noticeable luke warm, whilst setting 2 was red hot and left burn blisters on my palms. The seat was really comfortable up to a point, I could easily do 200 miles in comfort but found after that with the upright seated position the pressure on my backside become uncomfortable and added to rider fatigue. Finally it's not as pretty as the S nor does it sound as sweet.
This is my view and my opinion, others will disagree, and it is based on one RT only others may be different. However, sometimes if you really want a bike you need to just go out and buy it, get it out of your system. You can always sell it so if you shop around and get one at a good price then you'll have little to lose.