I've taught myself to double clutch on up and downshifts, thanks to the shithouse gearbox in the good ol' VL commy....now I'm getting a bit lazy with the skyline, but I certainly change slowly regardless.
I'll only ever throw it through the gears quickly when I'm driving hard, and then I will ALWAYS double clutch.
my box is a little notchy with 1st-2nd, and 2nd-3rd. Downshifts don't feel notchy, just tight. Strangely though, 2nd-3rd isn't a crunchy kinda feeling, but as it goes from neutral to third without the double-clutch, it feels like 3rd says "naww f*ck off" and gives it a little kick back towards neutral :S