As I recall (and I know I recall correctly because I checked), jyl asked for general info and in-use impressions of half-step with a 2 x 6 gearing. That's an ideal situation where it could be beneficial, and not especially comparable to any arrangement with a triple crank or a modern N >= 10 cassette. A triple crank might be a valid comparison except that with a granny gear you don't need an especially large cog, which means both your "single step" on the rear and your "half step" on the front can be pretty small.

Whatever you choose for total FW range or step-spacing, the front by definition should be about half that (as plotted on a log scale). If the rear steps are smaller then so will be half of that. Eventually you get half steps that are so small they are effectively no shift at all, so you don't want them too small. (Rings of 52 and 49 may make a numerically good half step with a corncob FW but in my non-racing experience it is pointless because the shift is too small to be significant.)

The other pertinent question is - how do you use it on the road? If you want a half step shift, which is the whole point, then you shift the front if it goes the way you want. If the front goes the wrong way then you also have to shift the rear one cog in the direction you want. It makes shifting convenient for fine changes. It does not give you a single-shift way to jump to a lower gear range; to do that you need to drop the RD into the right range and then start your fine tuning.