Dunno about anyone's favorite, but here are the rules for half-step. First, the tooth ratios of adjacent pairs of rear cogs are the same or nearly so. Second, the ratio between the two chainrings is half the average cog-pair ratio. If you look at the Sheldon Brown table for Khatful's amazing wide range system, you can it's ratios are nowhere near the same - it's not a HSG. And it's result is that he does not get all 14 speeds free of duplication. A real half-step will not give you any overlap. That's why for a 2x5 setup of yesteryear, it was desireable.