Overall I liked the movie. Kinda sad that it isn't doing better, because it means (like Justice League) it most likely won't have a sequel or any follow up.
It was Harley's movie, obviously, since her name was on the marquee. I loved her humor and antics, and that they gave her the hyena.
They did the character justice, and the closing credits "scene" was pure Harley.
As for the Birds, there were some great things and some mis-steps.
Dinah got the most air time, and my only real complaint was the costume should have been more comics accurate.
Loved the canary cry scene, but also was waiting for Harley to bust on her for not telling them about it sooner.
Huntress was hilarious based on her anger issues and social awkwardness. Her line about the crossbow at the restaurant made the entire movie audience belly laugh.
The movie needed MORE of her, since she didn't really take the stage until Act 3.
Renee was a great character, and I felt like she was near her comics depiction but unique in her own way.
Cass was the character that just really was "in name only". Honestly, based on her role, they should have made the character Harper/ Bluebird instead. (Street tough who comes from a hard life and broken family). I've never been much of a Cass fan, so it didn't bug me, other than that it was too different from who Cassandra Cain is supposed to be.
If there actually WAS some follow up to the movie, would love to see Barbara step in and take Cassandra under her wing. Grooming her to be the next Batgirl would be a move in the right direction. But based on the Box Office, looks unlikely we'll see any of the Birds again.