First off, make sure you watch ALL of season two before viewing RAZOR.
I loved the way it let us look back at a little history of a ship that isn't Galactica or Colonial One from where you'd be presently after watching season two.
You finally learn how Adm. Helena Cain became the hard-as-nails woman she was and how Gina (the imprisoned Six) came about being the person she is. Also, RAZOR gives the viewers a chance to see whether the rumors of the Pegasus are true or false.
