The anecdotal evidence is overwhelming. Rigorous studies are finally starting to catch up. I want to see properly controlled research before this gets either banned or commercialized beyond recognition.
The Imperial College double-blind study found that microdosers couldn't reliably distinguish active from placebo doses, which is a serious problem for the anecdotal evidence. If the effect is real, it might be largely expectancy-driven. That doesn't mean it doesn't work - placebo effects on cognition can be substantial - but it changes what we're claiming.
The expectancy issue is real and any good study design needs to grapple with it. But creativity is also notoriously hard to measure - most of the microdosing studies use instruments that weren't designed for this population or this effect size. Better measurement might find something the crude instruments miss.
What I'd want from a proper study: pre-registered, double-blind with active placebo, standardised creativity measures, and no industry funding. That study doesn't really exist yet.
I've done it. I'm not saying what I noticed but I'm saying I understand why people keep doing it.