I had floor boards on my 1200 Aspencade and my 1500 Aspencade. I am 6'4" and I found having the ability to move my feet around helped in some areas. I never had any transmission problems. If there is a problem, I would bet it is because the rider is resing his foot on the H/T shifter.
That being said, I took them off my 1500 and found the bike alot more fun to ride. Boards tend to hang lower and out from the stock pegs and they will drag the ground through a corner in a heart beat. It doesn't take much to find the ground with the boards. I have, however, not ridden an 1800 with boards, so I am not sure if they interfere with lean angle or not, anyone want to ring in on that issue.