I thought all the characters were great; I even liked Kylo. Only part I didn't like was the final fight, Rey turning the fight around like that seemed really silly and made it feel like there isn't a place for her character to climb to later. Despite what Gav said, Rey was a Mary Sue, but that's NOT always a bad thing; someone else pointed out earlier Leie was kind of one too but, the difference is, we knew Leie was a space princess who was in the rebellion and obviously had tons of education and experience. Rey? Not so much. (Like SOME engineering skills, I could get...Even piloting, but her learning all the force powers without a teacher, and all the languages and being so good at engineering she overshadowed even Han and Chewie on the falcon? Felt silly.)
I'm willing to bet, of course, it will be explained by Abrams stupid 'magic box' device, where we find out Rey was super specially trained to be the one and had her memory wiped. And that will make the trilogy feel a lot stronger for her as a character, but it still doesn't stop the fact that she felt a bit over the top in this stand alone film.
Also, they did try to focus on Kylo being injured, I know...Some people point to that as a reason the fight went the way it did..However the final actual round of fighting did a piss poor job of showing that, Rey just straight up kicked his ass, without his side hampering him.
In any case, this doesn't make Rey a bad character...but as said, the writing for her was ham fisted at times. It almost felt like Abrams was treating the trilogy as one long movie, and while that's cool, as a stand alone film it did leave parts of THIS film feeling odd. (Still very enjoyable though).