Passion is my favorite Sondheim show! I absolutely love it. I haven't seen the show live, but I have seen the filmed versions with Donna Murphy and Patti LuPone. I mainly love it for the score, but the story is also just very interesting and I like how it explores the ideas of passion and love.
I personally feel that the success of the show depends on the actress playing Fosca and how well she can convey the character. IMO Patti came across as very undignified and just extremely annoying in her portrayal (and it didn't help that Audra McDonald was just so likeable as Clara). I didn't connect to her at all like I had to Donna's Fosca, who I found much more dignified and sympathetic. I haven't seen any other actresses in the role, I'd be interested to see Judy Kuhn as was discussed above.
Funny enough, I showed my DVD of the filmed Broadway production to my husband and expected him to absolutely hate it because, let's face it, Passion is not a musical for everyone. He ended up loving it because the music was so good.
Jimmy, what are you doing here in the middle of the night? It's almost 9 PM!