First I must say that I'm not a huge fan of the story. I've read the book, seen the movies and I love the world Tolkien has created, but I don't like the story itself that much. Frodo and Sam always irritate me, and there are too many fights and battles which made me yawn especially during the second movie, so I was happy to notice that they had cut almost every battle from the musical and I could concentrate on admiring how they had created Middle-earth. The sets are amazing, they had changed the whole theatre to Middle-earth and before the show began the hobbits were partying and catching fireflies and everything among the audience. During the second intermission (just a quick break for a set change) Orcs came to run between the seats and scare people. There was some school class watching the show and the girls screamed like pigs and ran around in panic and all in all behaved like total idiots when the Orcs came. I don't really have words to describe the sets and costumes and Ents and Sauron's eye and so on, but they were brilliant. (There are photos and video and sound clips on the official site.) Especially Lothlorien was amazing.
The plot was of course very much shortened. They had left out all the big battles except Helm's Deep and the last battle outside the gates of Mordor, and the parts in the lands of men were cut to dying Boromir asking Aragorn to save his nameless father from the dark side, later Aragorn roaring something to the father and the father going "Wahh, you're my new king, I love you and will follow you to death!". Apparently a mixture of Denethor and Theoden, called simply the Steward of the Land of Men. No Eowyn, Grima Wormtongue or Faramir in sight. The story was still relatively logical and as easy to follow as the story in general can be. In fact, I think the cuts made only good to it, but I'm not a Tolkien fan so perhaps I'm not allowed to speak. ;)
The actors were mostly quite good. I didn't see any cast list but judging by photos I saw the full first cast, possibly apart from Merry and/or Pippin. Sometimes it felt like the actors just sang through their lines and lacked some feeling, but in general I had nothing to complain. Galadriel and Arwen had great voices, and I got a little crush on Aragorn, but it's no wonder because he's my favorite character, anyway. Gollum was absolutely amazing! His movements, voice, everything; the character basically made my jaw drop. I actually don't understand why most people laughed at his moving and the argue between Smeagol and Gollum, it did look funny but was after all very tragical. He resembled the Gollum in the movies a lot, but it's much creepier to see a real living person do the role than to watch a bunch of pixels moving. I don't know who the actor was but he was damn good.
The music was pretty much what you can expect from Värttinä and A. R. Rahman and most of the time it suited the scenes and characters well (happy folk songs for hobbits, chanting for elves, etc.). LotR isn't exactly a musical, it's more just a play with music though everyone has their solos and there's music in the background all the time. I can't remember most of the songs or melodies but in general I liked them, especially the cheerful Hobbit songs and Lothlorien.
All in all I definitely don't regret that I went to see the musical, I enjoyed it quite a lot, but it's not the best one I've ever seen. 'Nice' would be a good word for it, I think. I'd have to see it again to get an opinion about certain things because I've forgotten some scenes and everything was new to me, so I used much of the time just for staring at the wonders in front of me. And for glaring a couple of teenaged boys sitting next to me, they had problems in staying still and quiet, though I was pleased to see that my glares really worked and the nearest boy was wise enough to look ashamed for a while. :P