At one point the manuals recommended you use motor oil, but that was previous to honda developing a MTF. It was then updated to say only use motor oil as a temporary sollution till you are able to obtain some MTF.
If you want to use a synthetic MTF, try BG Syncroshift, or Redline. Some people report smoother shifting, reduced notchieness, and even very slight performance gains due to the lower drivetrain friction. on the other hand some people swear that it destroyed there tranny.
I am currently running redline, and have had no problems what so ever.
I have redline MTL and she shifts perfect...there are so many things that can go wrong with a trany it is easy to blame a transmission fluid change...your tranny will last just as long if not longer with redline...motor oils dose not belong in a tranny