I started paying them a couple years ago for my DynDNS service, and have had no trouble in that time. I'm glad they chose to keep the service rather than shutting it down. And I'm especially glad to see them charging a small fee for a valuable service, rather than running it for free: https://blog.pinboard.in/2011/12/don_t_be_a_free_user/
IMO they could have handled the transition to non-free better. But every time they took away some of the free stuff, you have seen popular outrage. They pissed off lots of people that could have been potential customers and I was one of them.
Their lowest price plan is 25$ per year. If I only would want the most basic feature, that is having 1 or 2 dynamic ip addresses bound to a specific DNS entry (not even wildcard or email redirection), that is too much. I would have gladly paid 5$ for that even if only to get rid of the 30 day renewal routine.
But when the time came for me to register my own domain, I didn't want DynDNS to do it. I've seen how they treated me when I was a non-paying customer.
Yeah, I thought about switching to a different provider for a few minutes but the time it would take is worth more than $20 to me. Plus, their free service has been working perfectly for years, so why switch now?