Today QuickDNS announced that they are closing down early next year, which is too bad if/when you don't want to use GratisDNS.
Time to put my money where my mouth is, it seems - so I created two cheap Linode VPS's and configured them to serve DNS for a couple of my domains, just to see how that will work out.
I have redelegated one of the domains to the new DNS servers, and still need to redelegate the other one, but I'll try to move that one too soon(ish), and we'll see how it goes.
Update: I have moved one of my .dk domains as well. Worked fine. Oh, and QuickDNS isn't closing after all(!) ⊗