After a bit of experience with scrum, one of the things I"ve come to appreciate is that it's not a one-size-fits-all methodology. I think the spirit of scrum (break work into chunks, have working code at each stake in the ground, define a project in terms of user stories, etc) is more important than the letter of the law, and being able to tailor the process to your current reality is more valuable than dogmatic adherence to some prescription.