I'm using Ruby on Rails stack for prismo development and i'm pretty happy with it. The biggest pro of using it is that mastodon is based on RoR as well so i can use a lot of code from it. On the other hand, ruby ecosystem lacks any libraries dedicated to work with AP so it's all about taking a lot of small pieces from mastodon and refactoring them for my needs.
When prismo is stable and ready, i would really love to make some ruby lib to make working with AP easier