I am a brand new 2014 A owner so I cannot speak from direct experience. I did quite a bit of research and lurking on the various FJR forums before making the leap back in November. What I came away with was a general concensus of ease of maintenance in general and an excellent track record of reliable, dependable longevity. First valve clearance check is scheduled at 26,000 miles, access is not as good as the ST, way better than the C14 and often no adjustments are required. Some have gone close to 100k miles and not needed attention. I don't see many complaints regarding valve clearance adjustments on the sites. All of the above for all three generations. The basic engine is unchanged since Gen I (Yamaha saw no need to do anything with the engine for the Gen III project although they studied many ways to improve performance including increasing displacement but felt the engineering was not worth the return - the engine shines as is).
Reputations of granite-like durability are pervasive. Many have started with Gen I machines and moved up as new generations have been introduced, some three or four times, very loyal.
As a motorcyclist of 50+ years and having ridden the big irons since the late 70s (Yamaha XS1100, Kawasaki C10 Concours, etc.) this is by far the finest motorcycle I have ever ridden in all respects. To me personally, the ST1300 is extremely close (my good, long time riding buddy has a 2006 and I have ridden it many, many times), an exceptionally fine motorcycle.
What the Gen IIIs bring to the table is state-of-the-art in "driveability" refinements and important upgrades in the handling and suspension (stiffer springs on the "A" for instance). Yamaha has spent many years developing and fine tuning the YCC-T (throttle-by-wire) and Traction Control on their high-end Grand Prix motorcycles and have intelligently moved these technologies out into ther flagship motorcycles (FJR and Tenere to name a couple). The Unified Braking System (Yamaha's version of linked brakes) is very well liked amongst the owners and seems invisible to riders, even the hard core canyon chargers.
Oil/filter changes are a breeze, not much else needs attention (air filter when required).
I let my son Steven take it for a ride for about 50 miles for the first time this past Sunday. I nearly had to pry it away from him to get it back.
It's all good.
Dan
[Edit to add:
Here is a link to a testimonial by a hard core, long time FJR owner that just moved up to a 2014 ES. Very interesting reading:
http://www.fjrforum.com/forum//index.php/topic/158660-creative-solution-to-aging-gen-1-issues/page-1 ]
