I have used a few different types of oil in mine all good oils IMO but I did notice a difference on how long they seemed to last when it comes to smooth shifting. So I use a expensive race oil and have discussed with the engineer at depth and this time I am trying another Grade of there oil. I must admit I used Mobile 1 4RT for almost 50,000 miles without a problem but once I went to different internals I noticed it seemed to break down more at least when it comes to shifting verses the oil/engine temperature so I switched to one with more aditives in it form both lubricity without hurting the wet clutch, higher themal breakdown ability, and more anti wear resistant. My choice use what you want and if you have a stocker do not worry about using the reccommended oil which I believe now days is Casteroil. Also Nev reccommends Motul 300V I believe and I would have no problem using what he reccommends nor would I have any problems using what Bob Carpenter Reccommends. In fact I use a brand Bob has reccommended before just a different grade.
As Nev would say good oil is cheaper then good engine parts. Anyone who wants to use something different then all I have to say is its your bike if you want to put a car tire on it go for it.
Myself I use Joe Gibbs Racing oil 
