I really enjoyed that film. It's not a masterpiece, like "Caligari" or "Nosferatu", but a good fun film anyway. Veidt and Jannings are wonderful. The first part, about Haroun al Rashid (played by Emil Jannings), is very humorous (and funny as well), with well written plot. The second part, about Ivan the Terrible (played by Conrad Veidt), is, in contrast, very dark and depressing. In my humble opinion, it is much better than Eisenstein's movie (which also steals shamelessly from it); for sure, Veidt is better than Cherkasov. The third story is something really weird: it starts and suddenly ends, like the crew ran out of money.
So, a lot of humour in the first part, a lot of "Russian gothic" ;-) in the second part, good acting, good plot, great sets -- if you like silent movies (especially expressionist silent movies), don't miss this one!
P.S. If you like silent movies and still haven't seen "Cabinet of Doctor Kaligari" and "Nosferatu, symphony of horror", see them first -- they are better than "Waxworks"!