This script had been laying around for quite some time, and when Allen decided to resurrect it, I'm SO glad he got Diane Keaton to join him for the filming. Their chemistry is still there, and so is Allen's wonderful neurotic schtick. The elevator scene is priceless. I also greatly enjoyed the tape-player skit with Allen's inimitable bumbling.
I think the film hiccups a bit when it abruptly switches to a film-noir ending. Mind you, I enjoyed the ending, especially the Welles homage, but I think this decidedly dark ending causes the whole vehicle to lose momentum.
All in all this great fun with plenty of zany suspense and the fabulous interplay of Allen and Keaton.