The previews were probably the best part of the movie. I thought most of it was improbable, contrary to other viewer's reactions, and was not as intense or as believable as the original Predator. I certainly didn't understand the doctor's soliloquy about being "normal" on that planet.
Overall, I really liked the movie and loved Scarlett. However, I don't feel the character development was absolutely necessary and slowed the movie down. I missed the constant rush afforded by the first installment.