My verdict is consistent with those mixed emotions. The choices made in terms of cutting the book down to a halfway reasonable length were fine, but I thought further editing was both possible and desirable. (Note that the first act was an hour and a half and the second a little over an hour.) I understand why various historic figures were included but there was a fair amount that could have been trimmed. Harry Houdini, in particular, could have been cut with no harm. Henry Ford could also have been eliminated, though he does get one of the livelier songs (albeit one that sounded far too similar to Sondheim's "Ballad of Czolgosz").
As for the music, I like the ragtime bits, but I thought there was too much grand sweeping faintly gospel-influenced material. I won't complain about a lack of hummable tunes (by definition, any piece of music is hummable), but there was nothing particularly memorable. And the lyrics struck me as particularly plebeian.
The performances were fine, with Christiane Noll powerful as Mother and Quentin Earl Darrington a convincing Coalhouse. I should also note Christopher Cox as the young boy, in a plum role for an 11 year old. The staging, however, also left something to be desired. I did like the living silhouettes effect for "Success," but much of the choreography struck me as too busy and unfocused. I also have a minor complaint about the costumes. Namely, it grated on me that Tateh wore a tallis (and a scarf-like one, rather than a shawl-like one) throughout the entire first act.
All in all, I guess I'd characterize the show as average. I suspect it would appeal more to fans of, say, "Les Miserables" or shows of that ilk.