Consensus in App Store reviews, which I've confirmed: it's buggy and feature-thin, but awesome awesome potential. Urgently needs an iOs version; they're working full-steam on iPad (hopefully by summer), but I hope it works half-decently on iPhone.
$24 for the advanced features seems worthy to support development of a swell idea, nicely designed and developed.
Non early-adopters: I'd suggest adding a reminder on your calendar for September 2018 or so to check and see if it's been sufficiently polished. I'd suspect App Store review rating will be ultra high or fading to mediocrity, depending on how this promising app fulfilled hopes. Of just use the basic free version, and see if you like it.