I actually generally liked the flashing effect. My only comments about the effect are in the 2:45 to 2:52 section. There are a lot of flashes which are a bit off-beat compared to the music. This would have been extremely cool if they lined up better with the music. Other than that though, I loved your use of effects in this one.
If you have trouble synchronizing the flashes to the music, there are a couple of ways to approach an effect like that.
You can study the waveform of the audio file and locate the exact time of the musical events you want to synchronize the flashes to. Offset the amount of time in the video before the music starts and BAM, you have the exact time.
You can use good old trial-and-error, adjusting the effects' timing until it feels right. Trust me, you'll know when it's right. If it doesn't have that *YES!* feeling, it's not right.
With a little math or a sense of knowing when the audio and visual events are lined up can take an effect like this to the next level!
As for the rest of the vid: Well done.
