I just finished the movie and honestly, it's pretty great. I'm a brony and grew up with FIM. I did feel as though Izzy was replacing Pinkie, but other than that the characters were all new and interesting. There were many references to what we all know and love as equestria with the mane six and all, which assured me we weren't leaving the old gen behind, just blazing a trail for a new and more modern one. The only thing I didn't really like was the ending with Sprout and whatever he was doin with being the leader of the Earth ponies. The way that ending all happened was sort of not expected, especially for MLP. The way I view an ending like that is sort of childish, which I know this is technically a children's show, but what made MLP so lovable was the fact that it wasn't like what we see in Kid's tv today.
I absolutely adore the animation style, setting, and the fact that everything is chronological and we get to see more technology being developed. This is the first time I've felt old (I'm only 15) when the characters called the old equestria we know, "ancient". It's cool, honestly lol. Now, while I love this and hope they continue to add on to this pretty amazing storyline, I'm just afraid of what the old fans will say... I hope they end up liking the new gen as well :)