I did the same thing with three 1GB Linode servers (spread out regionally). It is an excellent plugin.
I ended up switching to BuddyNS because the name resolution has been faster, it's cheaper (than 3 $5 instances) for fewer than 100 zones, and it was 3 fewer things for me to maintain. I didn't like the DigitalOcean plugin, the Azure one has limitations and Route 53 has the vanity irritations that you mentioned (which was the original reason I went with the Slave DNS Manager plugin).
I'm glad that you found a solution that works!
Cheers,
Daniel