If I make a 3D tetris game, I dont look at the scale at all.
If I make a FPS, I just create the level from models, taking the average c-babe-, warlock- and guard.mdl size as a reference for the height and scale of objects.
If I make a RTS, I do the same with smaller models (aprox. half the size of CBabe).

I never looked at the scales, but I was aware of it. But the 0.75 Cbabe / Meter is not in the poll so I choosed 32 Quants / Meter . I think most of the time I took the 32 Quants / Meter scale, though without actualy using it.