Now while I am not saying this is not a worthwhile change - better throttle pickup, improved mpg, yadda yadda - be a bit wary about it.
The 500 rpm drop has put my 800 right into the vibration zone. I like the way the bike goes with the 17 tooth pinion but my hand, wrist, elbow and shoulder don't.
I've been running the 17 tooth for about 8 months now and my osteopath has warned me that I'm in danger of causing permanent damage to my elbow and shoulder. So I'm currently waiting the arrival of a new 16 tooth sprocket from Touratech.
I'm also investigating anti-vibration solutions for the bars.
So make the change - but be prepared to change back.
Sorry to put a downer on it, but that's my experience.
SuperTed