A nice box set, but really should have also contained "The Plan" for it to be complete. It does however, include the Razor movie, and that is a definite bonus. There is also a booklet contained within the boxset that potentially contains spoilers in terms of revealing who some of the Cylon's may be, so for those buying this boxset with the intention of viewing it for the first time, or for watching it with others that haven't seen it, then don't read the booklet.
As regards the disks themselves, they are not going to blow you out of the water with the quality of their blu-ray definition, because of the way some of the footage was originally filmed to give it a a slightly grainy, "embedded reporter" type feeling to it. Indeed if you already have the DVD's of BSG, then I wouldn't bother investing in this box set, as you will gain no significant picture improvements.
The additional content, some unedited episodes and commentaries available in the set are nice to have, but I am sure that many people will just be buying this box set to have BSG in all its glory, in as few disks as possible.
In short, buy this if you don't already have the DVD's and you don't mind having to buy 'The Plan', separately.