Great. Opening. Sequence.
After the hook, it keeps going. It's a dark, slightly irreverent, constantly entertaining film. It made me jump (more than once) and made me laugh (more than once). Only occasionally did I find myself scoffing at Keanu or annoying plot inconsistencies. Overall the casting was inspired, and they spent wisely on effects, costumes and sets.
I wouldn't recommend this film to strict Catholics but otherwise, it's worth the $10.
[If you liked any or all of: Dogma, The Exorcist, Hellboy or the original Matrix, you'll likely enjoy Constantine.]