We use multiple providers based on some corporate standards, but they could not offer many of the features we needed.

I've used GoDaddy, BlueHost and a Network Solutions DNS but the TTLs weren't low enough to support failover (and they didn't offer it), so I switched. The Anycast DNS also offered better reliability than my previous DNS providers.

No, just the standard registrar supplied solution, that and Zoneedit which I used because it was free.