The thing that I don't like is that lot of these DNS hosts don't support using them for secondary DNS... It looks like deSEC is the same :/
I like using my own DNS server as a hidden primary because it lets me do bulk and programmatic updates more easily.
I'm using DNSMadeEasy for some of my important domains because they have the fastest servers, their service is really reliable, and major brands are using the same DNS servers so it seems like I can trust them. However, after being acquired by DigiCert, their prices went up over 10x... the $60/year plan I was on is now $675/year.
HE's free DNS supports secondary DNS but their reliability isn't great. DNSimple supports it but I'm over their limit of 100 records for some zones. Hexonet supports it but I couldn't figure out how to get it working and neither could their support.