What does Calendly do well? It's incredibly simple to set up and share with others. I had it up and running in just a few minutes, and love not having to email people back and forth to figure out dates and times.
What does Calendly not do well? It serves a simple purposes well, like online consultations, but if you have more complex needs (such as in-person and online, payments, etc), then other services are a better alternative.
What do you wish you had known about Calendly before using? Nothing. It's been a great tool, and I've recommended it to many others.
Have you used a competitor to Calendly? If so, how does it compare? Yes, I also have an Asana account as well. I think Asana is a better tool for more features and complex needs.