I’m also on Migadu for email, and I can say the experience has been pretty excellent. They have good instructions for setup stuff, and their pricing model is great. The pricing model has things in common with rsync.net, where they impose a soft limit on storage and reach out if you start exceeding it to talk about upgrading.
I do wonder if other mail providers will at some stage support jmap, it seems like it could take away some frustrations.
There are speed and developer experience improvements, and a whole bunch of it is there to optimise for mobile. They have some info in the FAQ on jmap.io. It’s something I won’t 100% take without any consideration - it is written by the fastmail Devs - but a modern stateless protocol is no bad thing.