DIDs always have a single point of failure. If you need a very reliable DID - use POTS.
That goes without saying.
My question related to DID providers with redundant connections to ISPs using BGP to automatically handle routing changes needed to reach CallWithUs. CallWithUs has three widely distributed locations. I want a DID provider with at least 3 BGP routed connections to the Internet.
I also use Vitelity. They are primarily a commercial provider but do provide service to residential users. They don't have a lot of web options like the other providers, but are pretty good. Voicemail and call blocking is offered.