I watched this yesterday.
I liked it very much. I wouldn't go as far to say I loved it because I thought it was an Episode IV tribute (the new empire, the new Death Star, the old mentor being killed, etc.), but I understand why JJ did it. It's miles ahead Episodes I, II and III, and I would rank it even higher than Return of the Jedi if it happens to grow on me. I was afraid Kylo Ren might become an inferior Darth Vader wannabe, but I was super relieved when he took off his mask because he gained a lot of personality to his character.
It was mentioned Rey became an all-powerful force user out of the blue and I found that kind of weird, but it would make sense with the 'there has been an awakening' thing Snoke said; and it's to be noted that her becoming a badass lightsaber user and beating Kylo to the ground was really amazing. The Darth Plagueis/Snoke theory is very interesting, and although it think it's very unlikely (they might as well be of the same alien race but entirely different people), it would be a cool way of linking the prequels with the new trilogy. I like the idea of him being the Palpatine of the new trilogy, but I hope there's more to him than 'I'm a powerful Dark Side user and I happen to be the leader of the First Order' because that would make him very much like the Emperor.
I LOVED the lightsaber battle. The scenery was incredible (snow/night) and I was super glad they didn't overdo the pyrotechnics. All 3 of them (Finn, Kylo and Ren) had this amateurish feel to them that made it very real. They actually hurt their opponents, instead of just cutting hands or chopping bodies in half. It was raw, it was exciting and it was epic without being a highly athletic Episode I Darth Maul jumping bonanza. Also, I think it was an amazing ending because it left be craving for more. I was super expecting a glorious ceremony like in Episode IV at the end, but was glad we didn't get one. The whole 'search for Luke' plot was one of the best things from the movie, I think.
All in all, excellent work JJ. Maybe you played a little bit too safely, but this is one Star Wars film I will watch many times in the near future (unlike Episodes I and II lel).