I did. The played with
feld (npub1swc…y2dn) using both the electron version and the iOS version.
iOS version is quite decent, desktop electron version needs to be polished. It's so slow my typing is not shown on the screen as I type.
But I can see a lot of promise on it. It can definitely do what Matrix can't by not creating a new standard for what's already there. I think the ingenuity behind it is its strength => email as the most authentic form of federation.
I like it
Needs fix: finding contacts, sharing contacts, it cannot be based just on QR sharing.