Okay, I used to use iMovie, you're making a big mistake using it. Grab a copy of final cut pro X, I take it you use a mac, correct me if I'm wrong though.
Honestly get hyper is an awesome song XD, I would give the video a 6/10, because thats pretty decent for an amateur video.
Editing skills need some work, and next time keyframe the replays, look up a thread on how to properly do it if you don't know, but trust me, keyframing will make your video 100% better.
overall, good for a first, hope you make an outstanding video some day
EDIT: slowing the replays down and speeding them up to go with the music works well, you can also try matching the hits to the sound of the music