I went to see this movie and I was suprised. It didn't totally suck. Sure I still think the old EU had better stories that could have been used and that it was in no way original as advertised but still a good movie in its own right.
Many of the problem I thought it had, have already been unveiled by other (stormtrooper helmets don't filter gas, Death Star on steroids etc) so I'll skip those and point some, in my opinion, bigger flaws of the movie.
The superweapon seems to be a one shot weapon. If it gets it's power by draining the star it's orbiting which is then destroyed in the process, how can it reload? It was built on a planet if I understood correctly and planets don't move like ships that can fly to another system. It may have more than one star, like Tatooine but still doesn't seem like a weapon that can be fired once every day or so.
Destruction of the New Republic capital had few problems in my opinion. The biggest is that how are Han and the other heroes able to see it so clearly in the sky while they're not even in the same system? The capital is in the Core (but not Coruscant as I thought) and Han and the rest are somewhere in the Western Reaches, on the Mid Rim section of it according to Wookiepedia. There is no way the light from the destruction of Hosnian Prime(
) would reach them as it does in the movie. Also when the First Order fires the weapon, it's destructive force of plasma or whatever strikes within seconds to a target that is on the Core while the weapon is in the Unknown Regions. And still has enough destructive force to destroy the entire system.
Then the state of the Galaxy. Is the First Order a splinter group that has separated from the Empire or is it what the Empire has become? Why is Leia part of the Resistance and not New Republic? How did the Galactic civil war end? I have more questions but those should suffice for now. So many unanswered questions. I know they will be answered in future movies and books and such but right now I feel there are huge gaps in the story. Meaning that the storyteller group or whatever it was that had the job to make sure the new canon story is consistent, are failing in that job. Also this new canon doens't seem very interesting.
Right now it seems that the entire story after Endor is:
Rebellion wins the war, Empire survives in the Unknown Regions, New Republic lives happily for 30 years, Skywalker tries to rebuild the Jedi Order, ONE student falls, Skywalker goes into exile, First Order emerges, Resistance forms to fight First Order, the Force awakens begins.
As for the characters, some were good while other not so much.
FN-2187, a highly trained stormtrooper indoctrinated from childhood to the principles of the First Order, defects after his first mission. Somehow that doens't seem realistic.
Poe Dameron, Resistances answer to Wedge Antilles. Enough said I think.
Rey, daughter of someone important (Han and Leia or Lukes perhaps) who meets Han Solo by accident and through him discovers her destiny as something greater than a mere scavenger. I too think she learns to control her powers rather quickly.
Kylo Ren, a fallen jedi who is conflicted of his choices. The problem I have with Kylo is his birthname, Ben. Why would Han and Leia name their kid after Obi-Wan? Leia never met him and Han knew him for like a day and they didn't really see eye to eye. A rather silly thing to complain I know.
Captain Phasma, her role in this movie was not as big as I thought and it was left a bit unclear wheter she survives.
General Hux seemed like Tarkin, without his commanding presence.
Snoke, what a stupid name. Also when I saw him in the movie I immediately thought that he is Palpatine reborn. But after the movie I learned that he had in fact been modeled after an early design of Palpatine so maybe it's just a coincidence.
This became a rather long post it seems. Sorry for that.