I'm just a user and I'm pretty happy with Migadu as well. I only contacted them once, and got a reply within a few hours. And a real reply, with technical details, written by someone who obviously understood the question very well.
The webmail is really basic though: it's basically Rainloop (https://www.rainloop.net/) without any plugin.
I also find the pricing logic a bit like it’s too good to be true, and am wary of providers who cannot sustain themselves.