DigitalOceans main selling point is not only the price and speed at which you setup a node. The main selling point is their freaking awesome support and their tutorial/help pages that help a lot of people with troubles that might have.
AWS, with its amazing stack size, cannot compare in those 2 departments IMO!
Its an issue for DigitalOcean that if someones trying to install MongoDB on Ubuntu they can still use any VPS provider they want. The instructions that DO provides are not platform specific to them.
I still do want DigitalOcean to succeed though, I think there great and still love there product. I think building an S3 competitor(Not expandable volume storage) would make them more competitive. Its still going to be really tough though, right now any side project is going to be default on LightSail.
Over the years I've opened up a number of tickets on $5-20/month droplets for all sorts of problems. Even problems that were my own fault, which I received answers through either blog posts they linked me to or step by step instructions on how to fix it.
On multiple occasions they helped me recover from catastrophic errors like having SSH locked down to only accept connections with SSH keys but the SSH service died because I ran out of disk space. In this case they can mount a recovery disk to your droplet which will let you get at your file system.
Aren't these available for free?