Cal.com has been amazing for me. I just love the UI and UX and how seamlessly everything works in cal. I have forgot the overpriced calendly I was using earlier.
Had an issue logging in and Peer (CEO) tended to the matter within the hour. I haven't had such responsive customer service so this was quite the experience. It's refreshing to find a customer-centric open source project do so well.
It's pretty easy to setup and offers a ton of nice features. I embed it on my website and have link to my profile in my email footer. Works very well, can't wait to use it even more in the upcoming months.