I have to say that the Bluray mastering is a whole new experience watching those films. Unlike the TOS films, they did not simply upscale the DVD-master but used the original to create those. GENERATIONS profits most of it, since the DVD master was never really good, as does INSURRECTION - the DVD version had some major flaws in several scenes.
The specials from the SE DVDs are all there, plus new content, including a 5th disc which has some interesting info, that is probably aimed at new fans... kind of a history lessen when it comes to Enterprises There are some really nice new CGI renders, featuring the Enterprise-F, Enterprise-J and all the known Enterprises!
You should get this set... experiencing those films in HD is like watching them for the first time.