My original opinion of M+ stands. I gave it a "B-" awhile back and still do.

I use it every flight, along with Oak Notes.
It is not awful.
It is not great.
It has a few very nice features, and some real duds.

Like everything tech-wise at Delta, the project pilots and non-pilot DT guys get very proud of their creation--which may or may not be a good product--and they also get very defensive whenever criticism is thrown their way. More than anything, they usually have little to no time or energy for legitimate pilot inputs and requests, but the second that a pilot one-ups them with a vastly superior app that easily outdoes the Delta-created app (iCrew Max, Oak Notes) they miraculously find the time and energy to immediately issue "cease and desist" orders. Sort of sad, really.

I'm still cautiously optimistic that M+ will one day be a superb app that we all use and praise. We're not there yet.