It fell into the same JJ Abrams-y overly fan servicey trap Star Trek: Into Darkness fell into... rehash of an existing story within the universe, far too many callbacks. Half the movie I felt like JJ Abrams was nudging me going.... "eh... eh?? See that? Death Star but BIGGER!"
The Good:
-The main characters are (mostly) developed well, Kylo Ren in particular seems like a realistic, flawed character, not just some overtly evil overlord, etc...I also like the concept of Fin being a stormtrooper with a conscience, that's something new in Star Wars.
-The film walked the line between seriousness and humour extremely well.
-The big "holy crap" moment near the end (I won't give it away for those that haven't seen it) was surprising, and risky, I was genuinely horrified, bravo for pulling a Joss Whedon...
-Big reliance on practical effects grounds the film in some semblance of reality.
-Final Scene gave me goosebumps.
The Bad:
-You like death stars? How about a DEATH PLANET???!?
-You liked the empire that we destroyed in ep6? How about the nearly identical First Order?
-You like the emperor? How about a new one.... uh.. but TALL!
-Why was Carrie Fisher in this film at all?
-Kylo Ren's relationship with his father is very undeveloped, perhaps that will be expanded upon in later films.
-Some of the CGI is downright terrible, like any scene involving Snoke.
-New emperor is named "Snoke" (Seriously?)
-Go home and watch ep4 again and you'll realize the script is nearly identical.
It still averages out to a good Star Wars film, but IMHO they need to do much better for Ep8/9.