gdnsd looks awesome, I just found it a few days ago. We will probably need a combination of manually assigned geo areas + fallback on automatic assignment based on distance.
The failover modules can be a little awkward to wrap your head around at first. There's simple, weighted and multi failover modules, and sometimes the one you want isn't the one you'd expect!
Aside from that I can't fault it. We're still running a pre-1.0 version (around a year or so old) and it's not skipped a beat.
Anything to keep in mind when using it?