This started out as a reply to Kelly's last comment two posts down, and then I realized it was too long, so now it is a post!
I was just discussing "The End" with Art Boy over breakfast and trying to explain my frustration with the series. Much as I love it, it often feels as though Mr. Snicket is writing a long joke more than writing a story, and long jokes can wear thin. Sometimes it's not quite cartoony enough. My favorite installment is still "The Wide Window," which I think just strikes the perfect balance between the dreary (cold cucumber soup) and the ridiculous (Captain Sham).
Anyway, "The End" is similar in tone to the last few books. It introduces a bunch of new complications that Mr. Snicket obviously finds funny, but that don't answer the questions you've had. There are a couple of answers and some surprising revelations, and a satisfactory moving-forward of things at the end (I thought), but on the whole it was bittersweet. So many series subplots are just allowed to drop. It's probably best to warn you that the entire book takes place on an island. I kept waiting for them to leave and go back to some of the other places in the books, but they don't. It's certainly worth reading, though, if you've come this far.
The series never really recaptured my heart after "The Austere Academy." "The Slippery Slope" came close, partly because of the development of Sunny. I think Mr. Wufflekins is right about her: she could ditch the others and be fine on her own.