With negligible tolerance, I find as little as .5 or even .333 mg can be surprisingly useful, and that's while using 3-FPM on a daily basis (though only at 'therapeutic' doses (80mg/day) taken slowly throughout the morning.) It's not enough to do anything particularly noticeable while awake and won't reliably get me to sleep much, if at all, faster than I would otherwise but it does generally make for a really good deep sleep without any grogginess or too much risk of oversleeping the next morning (the latter is always an issue for me if I take it when sleep deprived or fatigued.) That added quality of sleep really does seem to make a fair bit of difference - easily as much as an extra hour or so of unaltered sleep would.
EDIT: oops, that was meant as an addition to your prior post but in terms of using it while out and about, I don't really find it all that useful for anything on its own - it doesn't even do much to attenuate my social anxiety. .5-1mg can go quite nicely with a beer or two and/or a smoke but either combo is a recipe for monging out, so not great in public (particularly alcohol due to added risk of amnesia/stupidity) and not something you'd want to make a habit of.
