Form - The film plays with the film-within-a-film concept to great effect. For about ten minutes, the camera swoops around a theater, showing people watching the film that we're also watching. It's stupid, but trippy. A motorcycle sequence functions as the films climax, featuring tons of jumping demons, quick cuts, and stylish shots. The ending is also genius, the same two shots over and over again until something horribly unexpected, yet totally inconsequential, happens.
F/X - Gore, gore, and gore. Excluding the amazing stunt work throughout and the occasional helicopter busting through ceilings.
Acting - Great to okay. A pimp with a particularly embarrassing dub job is cinema gold, but the relatively high production values and great effects just make you wish they hired some okay American actors.
Mise en scene - All of the props are very utilitarian: if there's a car, a motorcycle, an alley, a sword, a mask, or anything else, it winds up somehow being significant to the story. An interesting touch.
Quotables - Many. The aforementioned pimp is full of them, and so are a gaggle of punk rockers who stumble into the theater.
Cool stuff - Drug abuse, Evil Dead rip-off creatures, helicopters, and an all-action approach to storytelling. For many people, this is probably the high point of Italian horror. Not for me, but close.