The trailer won't do the movie justice, I think.
Branagh is one of the finest actors in Hollywood, and had directed some really cinematic films and is a stickler for detail and character development.
He has directed Shakespeare adaptations, and I think his vision and passion for Shakespeare will give the film it's period piece feel when they're in Asgard.
Probably the greatest film he directed is Mary Shelley's Frankenstein.
I'm a little concerned because he's never directed an action film, but I think the elegance he focuses on in his films will sell Thor to people who like Medieval war stories and period pieces.