(watching via youtube)
I wasn't convinced on the anime mix until much later. The beginning 20 seconds were very weird because the anime used at that point just didn't belong together. But they could have, and later on I think they did. However, adding Eureka Seven in the last 45 seconds and making it the main anime featured there wasn't a good idea. I would have either added it earlier, or just kept on going with the anime you already had.
Up until :17 is alright. It's kind of boring because it's the same scenes of Angel over and over.

There's a flash at this point which makes sense; I understand why you put it there. However, this flash, as well as every other one in your video, go over the black bars you have, and it looks cheap. The more you learn about Aspect Ratio and such then this won't happen. If you want the bars there (sometimes I like them too) then you need to make sure in pan/crop in vegas that the top and bottom dotted lines are drug down to the edge of the scenes (past the black bars.) I'm assuming you have these bars on your scenes, or you just have the project file in the wrong aspect ratio, I'm not sure. This is if you're using Vegas. If you're using wmm, don't think there's anything you can do. Point being: white flashes that go over black bars are attractiveness. If you can, try and make sure in future videos it doesn't happen.
From :17 to :43 is actually alright. The pacing is fine, and the clip choice is fine. The clips match the lyrics, so not much more needs to be said. However, and this is just a personal thing, 5cm appears quite odd next to Anohana and the rest of these anime. Eventually you get used to it, but at this point in the amv you don't.
At :47, after that scene, I was expecting more Anohana, but then you had this other anime, which would be alright, if the next scene weren't so long. It should have been cut down in the beginning and you could have had more scenes of Anohana in there maybe. Also, the fuzzy border on this clip is ugly and should be gotten rid of in my opinion. It's not really necessary.
:54-:48, good job with the cuts. This scene also really matches the song. However, you really notice the frame blending in this scene (it's in all of the others as well.) There may or may not be blending in the original clips, I'm guessing there might be because of the quality of them, but if not it's likely a rendering issue. You probably didn't set the frame rate up right, and the anime might have different ones as well.
Scene at 1:04 of Otonashi falling is fine, except that him grabbing at the air mad me laugh. I would have used a different scene. Kind of messed up the mood

Also another too-long scene.
Scene at 1:13 is actually a tad long too.
1:25-1:37 well done!

Definitely matches the pacing of the song very well. However, I think you zoomed in a bit too much for the zoom-out sequence. I would zoom out just a tad, because as it is it looks too harsh. Very good part though,
1:43- 2:09 Another instance in which you have one scene of Anohana then over 20 seconds of 5cm following. I think there needs to be a slight consistency with how often you switch between anime, which is usually judged upon based on the format of the song (chorus, verses, etc.) This part is quite boring because of all the 5cm, to me.
Overlays at 1:59 were a nice attempt; they matched the beat of the song. However, it just didn't look good.
2:13-2:19 is very nice. However, from 2:20 it's a bit too slow; you just entered a quicker-paced section of the song, it should be quicker. at 2:24-2:33, some nice-paced segments mixed with too-slow ones. Too much Guilty Crown too. I'm alright with where it was introduced though; it's later in the amv, but as late as it should be to be alright.
2:33-2:45, tad slow.
Drums at 2:57 were unnecessary. I mean, it fits technically, but not emotionally. Also, an orphan frame at the end.
3:13 to end: pacing is good. Don't like the introduction of Eureka, really out of place.
Overall: Emotion is spot on.

The pace of the amv overall is very good, especially for being one of your early videos. The anime mix starts to work toward the middle: 5cm makes it a bit boring, Eureka Seven added too late. Make sure the flashes don't cross into the black bars. Frame blending and quality need to be worked on.
Nicely done though

Keep practicing, and a lot of other things will come naturally, like when to cut a scene, etc.