My primary reason for going to see this was that I'd read it was written by the same folks who were responsible for The Musical of Musicals: The Musical which I had really enjoyed. The concept of this show is pretty simple. Take the familiar Dickens story and throw in parodies of Broadway songs along the way. So it opens with A Broadway Christmas Carol Tonight (to the tune of Comedy Tonight and continues with Scrooge singing "I'm in the Money" and so on. Most of the fun is figuring out what is being parodied, especially as other little tidbits get thrown in. For example, Scrooge explains that his only relative is his nephew, "F-R-E-D, Fred." (For those who don't recognize that, listen to the cast recording of Once Upon a Mattress.
The show was reasonably entertaining but not as brilliant as its predecessor. Part of the problem is that A Christmas Carol is a sappy sentimental piece to begin with. And many of the musical selections are too brief or too obvious to really hit the mark, e.g. Tiny Tim singing, "I'm going to walk tomorrow." One does have to admire the four person cast, who work awfully hard at this. Peter Boyer as Scrooge may have had the easiest job. Both Donna Migliaccio (as The Woman Who Isn't Scrooge) and Mathhew A. Anderson (as The Man Who Isn't Scrooge) play a large number of parts, with lots of quick costume changes. And even Aaron Broderick (The Man Behind the Piano) gets some extra duties.
All in all, it's far from essential, but is, at least, not quite as sappy as Dickens.