It will be hard to review this without giving any spoilers especially since a lot of things have happened. But I will try to.
This final episode of the first season starts out a little slow where Barry is asked to make a very important decision. I think it's one of the things I like about this show. That not everything is rushed through and that sometimes the characters do stop and ponder about matters they should ponder. There are quite a few touching moments that make you understand what is at stake for Barry and co. You see that Barry and other characters have come a long way and that they have been through a lot. This is one of those shows where it is rewarding to pay attention to them since most of them do serve a purpose. You either like or dislike them and because of that you do feel invested. So it was nice to see some of the little sub plots get resolved. Then when the moment has arrived for Barry / The Flash to take action everything shifts into high gear and you get to witness multiple spectacular and very dramatic events that make you sit at the edge of your seat because the incredible fast pace of it all barely gives you the chance to take it all in. And just when you thought you can everything shifts into an even higher gear and ends with one major cliffhanger ending. Now for me personally this last turn so to say was unnecessary but I think it makes sense in relation to some of the events that played directly before that. Maybe there is much more to it which we will undoubtedly find out in the second season. In any case it's epic and an ending that belongs in a show about super heroes.
This season finale was very satisfying and it confirmed what I knew about the show and it makes me look forward to the following season(s). I have faith in these writers and hope they will maintain the high level of quality they have put into this show.