So let me say this first, I did not see the show. I listened to the entire sound track on Youtube with the INTENT to buy many of the songs. I'm also a faithful member of the faith that this show is lampooning, having gone on the mission that each elder on there has done.
So, let's get right too it. Is it good music? Yes. Is it funny? Extremely. Is it offensive? It's from the creators of South Park. If that doesn't tell you anything, you need to watch an episode now. In any case, the songs are genuinely well put together and there's a LOT of substance to the lyrics, such as how Elder Cunningham making up bits about the titular Book to stop natives from raping babies, then a later musical number equating baptism as a metaphor for sex being a clever way of pointing out that Mormon's do not believe in baptizing infants, while also being so offensive and funny that you really gotta give it to Mr. Parker and Mr. Stone for their wit and genius.
Numbers such as 'You and Me (but Mostly Me)' and 'Hello', do a brilliant job of parodying Missionaries and Missions...actually, the entire sound track is a BRILLIANT lampoon of the Mission. I mean, seriously. The humor is so accurate it's kind of scary. I was on my mission, and how accurate the humor was (as well as the South Park episode depicting our religion), that a rumor was started that the creators were ex-Mormon's. I later found out this wasn't true, but dang, do they know their stuff.
If I had to put out a negative feeling about the show, YMMV completely counts here, but the previously mentioned number 'Baptize Me' made me feel rather uncomfortable, as a missionary, I've baptized several people, including a 14 year old boy and a woman who looked to be in her Nineties. The images it put in my head were NOT pleasant. However, don't let this stop you from enjoying the Musical.
Again, I really should consider buying a ticket if I ever get a chance to see it. I think everyone should, really. ESPECIALLY members of the church. It would give you a laugh and surprising insight into how we're seen by the rest of the world ('Turn It Off' was VERY illuminating to me in that regard). If you aren't Mormon, but are curious, see it. Then go to wikipedia to look stuff up. If you're still curious, find our missionaries. Or go to Mormon.or-YES I'M SOLICITING WHAT OF IT?!?