YankeeFan...don't know how recently you've seen the Frogs but since the opening nearly everyone seeing it and reporting back has said that Act II is much stronger now. I saw it a couple of weeks ago and found that since previews they had cut quite a bit and the show is tight and funny.
As for poor Nathan...the box office on this show is doing fine. It would have been great if everyone loved it, but they predicted mixed reviews from the beginning since it is not 'a funny thing happened on the way to athens' nor is it classic Lane or classic Sondheim...still a good show.
"Life is a lesson in humility"