I like that it is easy to use, has great support from their team (which we've never needed), can be deployed in minutes without much configuration required - so you don't have time spent getting your environment set up properly or learning how all of this works! We are able to easily deploy new networks with very little effort using Plumgrid's simple UI/CLI tools as well as API calls when necessary.
The only thing about Plumbrid which could potentially improve would probably be documentation around some aspects such as creating subnets within VPCs but otherwise everything was good!