Fred...i use Rotella T Triple Protection 15W40 conventional. I have used it for at least 300K miles on various bikes... '04 FJR, '08 FJR, '03 FZ1, '04 Vstrom 650, '08 Suzuki GSX650F,and '04 Ninja 250....NEVER had a problem, bikes always shifted smoothly. Fast forward to Jan 12, 2013. Picked up my new '13 FJR 1300..bike shifted smoothly till I changed out the oil at 648 miles...put in Rotella T as usual...almost immediately noticed the shifting was notchy and hard, especially on the down shifts. Ran it for a bit, then decided to change oil again at about 1200 miles...put in Rotella T once again...now it seems to be getting even worse. Shifting from 5th to 4th is a bitch. Pull in clutch handle, and sometimes it takes a second to disengage. Blipping the throttle on the downshift seems to "un stick" the clutch.
At this point, before I take it in for warranty work, I will change out to either Yamalube or Amsoil synthetic.