I saw it a couple of weeks ago. I'll be honest and say it was OK, but not great. Glinda the Good witch was played very well, with a number of knowing grins and comments to the audience.
However, there's a contrived story line which in a politically correct way alters the original Wizard of Oz history, and amends what you know from the original film/book, to get them to fit in with what the producers want to say.
From a technical viewpoint, the dancing and singing were very good on the whole, although some of the crowd scenes could have been handled better. However there's only 1 song which had any vaguely memorable hooks in it.
I only paid £30 a seat for very good seats so I'll be generous and say as a musical it only rates 6 out of 10.