As a professional musician I use this app on my iPad Pro for my daily conducting /playing/ practicing/ studying/ accompanying/ teaching work at the podium, as well as the piano and the trombone. I simply scan my music using TurboScan (an indispensable app!) and send it to Dropbox, then download it to the PiaScore app. Then I compile set lists for each day, as well as tags to quickly find music for each of the many categories I need for my eclectic schedule.
When I first starting using this app about six months ago, I noticed that adding annotations slowed down the page-turning process, so since that time I have avoided using annotations in scores I use for rehearsal or performance (annotations for study is ok as I can make an extra copy of a PDF and mark it up for that purpose.) If PiaScore has improved upon this bug I havent read about it, but since I cant take the chance of a slow page turn in performance I simply avoid annotations in those scores altogether.
All in all an terrific app — if PiaScore would (or has) fixed the annotation-page-turn problem then I would recommend it unreservedly!