Hey all,
I owned two FJRs in the past few years - great bikes! Lots of power, good handling, decent ergonomics, great fuel economy. I traded my 2006 FJR in for a 2008 Kawasaki Concours 14 - also a very worthy bike! I wrote a fairly lengthy comparison thread here (and on an FJR forum and a Concours 14 forum) a few years ago.... wonder if those comparisons are still around? To sum it up in a nutshell, I would characterize the FJR and the C-14 as Sport-Touring, whereas the ST 1300 would be more Touring-Sport. All are excellent bikes but the FJR and the C-14 definitely accelerate faster than the ST 1300. The FJR seems like the sportiest of the bunch, closely followed by the C-14 then more distantly followed by the ST 1300. (I have never actually owned a ST1300, and my riding impressions of it are based on about 2 hours of riding experience.) I did find the wind protection was better on the C-14 though. Aftermarket windscreens are a must.... even the taller OEM screens are a big improvement over the stock small screens. Rear vision through the mirrors is poor on the later model FJRs and the C-14 though (but you learn to live with it.) .... the earlier model FJRs (2004-2005) can use the wider FZ1 mirrors which are a big improvement.
A few people have mentioned heat issues.... you have to expect that with a huge powerful engine tucked between your legs. These engines put out a bit of heat but I never found it to be a problem - even in 30C - 35C weather. (actually can be quite welcome in Canada in the fall.)
Fuel economy is similar on the FJR and the C-14 - on a recent 3500 km trip with the C-14, I averaged 5L/100km... quite respectable!
If you have any specific questions, send me a PM.