More of a lurker here, but since Ms. Wolfe is a new addition to the show, I thought I'd throw in my $.02.
Familiar only with the Jessie Mueller's vocals on the cast recording and various clips of Mueller and Sara Bareilles online, I would agree with those who said Betsy Wolfe's Jenna is a little less "gritty" than her predecessors. That said, her voice on Saturday afternoon was beautiful. While I had seen her a few years ago in "Edwin Drood," that show left very little impression upon me, so I took this as my introduction to Wolfe and I was thoroughly impressed as was the rest of the group of nine with whom I attended "Waitress" this past week. Her acting, though less "gritty," worked for the character -- for me, at least.
My only qualm which was agreed with by my brother was that the relationship between Jenna and Pomatter in Act I felt a little underdeveloped. When "Bad Idea" rolls around, there wasn't quite that palpable sexual chemistry that seemed like was necessary for the song to really succeed. When the curtain rose for Act II, however, and by the time "You Matter to Me" came into play, their relationship felt a little more grounded and fully realized. I don't know if that's an issue with the play itself or with the performers still trying to get their connection down, but that was really my only issue with the production which, overall, was an incredibly enjoyable experience.