Saw the tour twice in Seattle (second Tuesday and third Tuesday).
The first time I saw it, Alice was out and Pearl was on. Pearl did a really good job, and having an Asian actress play Diana really put an interesting spin on the family. She was pretty strong voiced, and still complemented the rest of the cast.
The second time I saw it, Alice was back in, and Jeremy Kusnier was out, Jason Watson played the Dr.s. Alice sounded like she was in better voice than how some of the others described her. I was trying to figure out what her voice sounded like, and the best way to explain it is, you know that feeling you get when you're choked up and about to cry, and your voice gets a little out of control. That's what Alice's voice was like while singing. Which worked O.K. for me for the most part. Her regular speaking voice was fine, and her acting was great, a little more off kilter than Pearl's performance.
As for the other cast memebers, I really likes Asa and Emma, and felt they did put their all into the roles, and I found myself really sympathizing with them. Preston I really liked (and I like his voice better than Adam's on the cast album).
As for the two doctors, I liked Jeremy's singing voice better, it was a little more forceful. Jason's singing and acting was a little more "lightweight", but Jason I thought was "sexier" in the role of Dr. Madden, which I liked, putting that added tension to the relationship between Diana and Dr. Madden.
I think the weakest cast member is Curt. Sure, he looks the part, but I found his singing voice a little too nasal to my liking, and I had this constant problem with him. Whenever he sings "I'm alive, I'm alive, I am so alive", the very first "alive" he never enunciates it well, though he does the second time he sings the word. It sounds like he's singing "I'm a lies". I noticed this from the very beginning, but my sister (who also saw both shows with me), did not notice this until after the second time when I talked to her about it during intermission. She really noticed it then during the reprise of "I'm Alive" in act 2.
But it's a great show (I did end up crying both times I saw it), and it really resonated with me.
Xanadu! Can't cry on cue!