Of course a "typical" driver would do none of these efficiency enhancing driving techniques or mods, so a fully functional system would be to their benefit.
But you're right - one of the first mods I'll do after fixing the pack will be installing the clutch switch mod to shut it all off again
... well, to disable assist most of the time, as you say.
Of course, sometimes you just can't coast to decelerate, in which case regen will be most welcome (as will be the max-regen switch mod). I will say I definitely wish I had regen every time I have to hit the binders while driving this car.
EDIT: and you're right - that quick, quiet IMA engine start is pretty slick compared to the archaic 12v cranker.