This was one of the most emotional episodes of this show. Both the medical stories and the personal storylines of the characters were extremely moving. Initially it seemed like everyone would survive the car crash, but things soon got complicated. Alex really stepped up to the plate, it was nice to see him finally proving himself to Addison. The scene between the father and the intern who caused the crash was just gut-wrenching.
Derek acted horribly towards Meredith, so it was nice to see her finally putting him in his place. That was a really great monologue. Although it's completely obvious why Derek is acting this way: He's totally in love with her and sooooo jealous!
And I really love Denny, but no good can come out of that.