Caught this today and overall had a really great time.
Cast was uniformly excellent. Emily Blunt was stunning, if not given quite enough to do and work off of. Comparisons to Julie Andrews are pointless, as Julie had better, more memorable material to work off of (and, well, she's Julie Andrews) but Emily has made her own mark on a role that was seemingly owned by Dame Andrews.Spectacular singing from her as well. I enjoyed Lin Manuel-Miranda MUCH more than I thought I would. At first I was confused by his casting, but he comes off very charming and endearing on screen. Agree that Ben Wishaw was the unsung hero of this cast. Emily and Lin were great, but without Ben's range of emotion and vulnerability, they would have come off weaker than they did.
I thought the movie started off slowly, but picked up quickly when Mary Poppins appeared. After Mary Poppins arrived, the film flew by, until Meryl's scene. I love Meryl, and she was great with what she had, but I was just sitting there thinking "Why?". It didn't advance the already thin plot at all. Other than that my only other complaint in terms of pacing was that the dancing scene went on for too long, without giving anything new for the audience to watch. Loved seeing Angela Lansbury on screen again.
The score was pleasant, if mostly forgettable. There were no songs that were painful to sit through, but none that stood out to me, besides "Trip to a Little Light Fantastic" and "Nowhere to go But Up". I didn't mind the rapping/patter, and did enjoy that number, although I could never hum you the melody.
Overall, great performances and singing, a thin but fun plot with a pleasant score to go along.