How many people are actively working on it and maintaining it? From my experiences with Vagrant and Packer, I get the feeling that there is not much development effort (by Hashicorp employees) allocated to the free Hashicorp products so I hesitate to even consider using Consul.

Vagrant and Packer feel like early alphas and while there is little competition, I do not feel comfortable using them. Because of this bad experience in the past, I have not even tried out Consul and Vault and am unlikely to do so in the future.