Saw this last night, and I have to say it's a fun night in the theater. I don't have much to add to StageDoor3's plot summary as he nailed it. This is more in the vein of Momma, Mia rather than Jersey Boys. There is some fun staging and I will add the songs are very well integrated in the show and for the most part work extremely well. I can't remember an audience this amped up for a show in a while, and for the target audience it delivers. Is it perfect? Definitely needs some fine tuning (a couple of the songs don't land or feel awkwardly placed, however, they are the exception). They are still tinkering as you expect.
The cast is uniformly excellent selling a thin plot. All four of the primary leads (Paul Alexander Nolan, Charlie Pollock, Alison Luff, and Lisa Howard) are excellent. Particular kudos to Mr. Nolan. I've seen him in a few shows now, and he really is giving a charismatic performance (this could be a star maker for him). His voice works perfectly on these songs, and the duets with Ms. Luff are wonderful. I enjoyed Ms. Luff's performance, but she is not given the best songs (in my opinion). She really is in need of an "I want" type song to cut loose on. Mr. Pollock and Ms. Howard provide the "B" couple roles and are charming and fun.
Quite honestly, I believe the market for this will be more in regional and on tour. I can see it doing okay in New York, but most of the songs are not as well known as in Momma, Mia, so I don't think it will have the legs. Not sure I'd pay upwards of $100 plus for a ticket, but then I'm not a Parrothead. They are definitely planning on taking this to Broadway after a few more stops on the road (per the very nice lady at the concession stand). So is this mind blowing theater? No. Is this a totally fun, pretty mindless evening to enjoy and forget your cares? Pretty, much.