Done 15k miles on my 2nd hand Dec '05 1200RT from Vines (Guildford) without ANY reliability problems.
Originally wanted a K1200S, but the pillion comfort was not much better than my Firestorm, so got the R1200RT old mans tourer!
Can't say anything bad about it, but can't say much good about it? Terrific all rounder, but primarily designed as a one or two up long distance tourer.
I use it daily throughout the year for work and the panniers and grip heaters are brilliant.
Some quality issues, but items replaced under warranty, watch out for corrosion on footpeg support plate, engine front plate and fork stanchion legs.
Bridgestone 020's better then the Conti Road Attack's, will try the B021's at next change.
Have kept my sports bike for more spirited rides, but will always go on the BM when distance/luggage/rain are involved.
Wind protection very good with the height adjustable screen, cruising at 80+ you can read a newspaper behind the screen! Given the choice purchase choice again, I would still go for the K1200S, but it is not as good as the RT for everyday and touring use.
Handling surprisingly good once you get used to the bouncy suspension (in comparison to a sports bike) and very stable at all speeds.
Main niggle at the moment is how to turn off the indicator auto-cancel 'feature', which is a pain in the a**e. Dealer says that they will have a look at cancelling it through the diagnostics at next service.
If you want a comfy, quick (but not fast), ultra tourer, then give one a test ride. Bear in mind, if you haven't ridden a beemer, then it can take at least 500 miles to acclimatise to them (that's just the indicator switches), so don't expect miracles during a test ride.