jimmuller 

My UO8 came from the factory with 52-36 rings and 14-16-19-22-26 FW, which produces a 2 1/2-step crossover. As I understand it this what is meant by Alpine; well, the Peugeot catalog called it Alpine gearing. I could use it as a crossover system, but there were few reasons to. The cogs were close enough together that the in-between ratios weren't needed. If I (or the generic "you") needed one of those ratios, the road might change and the opportunity be gone before I ever got the shift finished! Instead, the front shift was a by-golly-go-into-LOW range shifter, so that's how I used it.

But the real reason I (or "you") don't do crossover shifting with an Alpine is that at least for a 5-spd FW there are only two mid-point ratios available on each ring anyway, and one of each is an extreme cross-chain combination. There just weren't many useful gears available!

Back to half-step utility, it was suggested a page or so ago that you actually shift most on the rear, and the front is just for fine-tuning so a very small front change is okay, that you really didn't use the front to get in-between ratios. It seems to me that that is exactly what "fine-tuning" does, gets a ratio better than the one you just got and better than the one you just left. Which is to say, one in between the two.

It also seems to me that if you find your front shift beneficial even if it is just a small change, then you'd do it more often, not less. Road grade, wind, and similar things that affect speed or your pedal load a small amount occur more frequently than things which affect your load a lot. Of course around here the load changes a lot quite often, but that just make small shifts less useful so that a larger front shift is more desirable anyway.

All of which is to say a half-step makes sense (to me) only if the cogs are far enough apart to make the front shift useful.
But what do I know?