The main issue is that B2B supports it pretty well, but if you need to say, do something like add an extra attribute dynamically to the JWT tokens, or allow automatic migration from a legacy IdP on first logon, you are forced to use B2C and Custom Policies which are effectively a programming language defined in XML and which are quite nasty to use. In addition to that, B2C doesn’t fully implement all of OIDC so things like client credential flow are still in “Preview” at the moment. Deployment of custom policies is also only by use of a “Preview” API too. It didn’t feel mature enough to me.

Unless I force the access token to be refreshed 20 or 30 minutes before the stated expiry time then the session gets killed off.

It works now, but there was a lot of head scratching and trail-and-error before I found out what was going on.