Here's what I love about From Dusk Till Dawn: it has a complete shift in tone halfway through. You're going along watching a movie about these two criminals and their hostages and then suddenly Bang! it's a crazy action movie about hyperviolent vampires! Look out! It's Fred Williamson and Tom Savini! Whee!
I like that because it's just not something you see in movies. Normally, the pace of the first scene is more or less the pace they shoot for for the whole thing. Wouldn't it be great if you were watching a slow, suspenseful movie (like, say, The Haunting) where it gets more and more tense waiting for something to happen, and then suddenly it turns into 28 Days Later? Wouldn't that come as a bigger shock?
I also, obviously, enjoy Salma Hayek's performance. Rhias says that Ms. Hayek claims to have been mocked as a child and called a "hideous dwarf". I can't see it, myself.