tezza88,
I've had one of the Motul gear oils (can't remember which) in the old CB7 box for a couple of years. When I changed the oil the shift instantly became noticably slicker, but I don't know whether this was because the oil was synthetic or just because it was new, as opposed to what was probably 15 year old engine oil (not even the Honda MTF).

I do have some slight synchro weakness on third gear, but it's only crunches if I make a careless shift. I now have a long lever (about 100mm longer than stock), but still have a much shorter than stock shift throw. Shift lever is also bent to the right and the shift knob is now very conveniently placed so the left hand just drops onto it with little motion and the shift is 'snick-click'. Shift effort is a bit higher than stock, which is light anyway. I've also replaced the shift cable rubber bushes with metal bushes, I can now feel the metal bits inside the box through the lever!