Wow! Great video. Could not have been easy to get!
Thank you. It surely wasn't.
Couple of things (just my opinions):
1) Some scenes go on too long.
Agreed. I had multiple more videos that didn't end up going in, because they all start looking roughly the same.
2) I think the original start of the bird chirps (at opening) is great but they get old fast.
Not sure what to do about that, besides choose a different track. Ideas?
3) Considering the music, I would have used fading instead of hard cuts between scenes.
I noticed the same thing on playback. I'm editing in some changes. Stay tuned. 
4) Noticed that the image brightness would flicker when focus etc changes (think this is how video mode works - camera goes through agc cycle when focus changes?).
The camera was on full manual. D-lighting was off. I don't know why that happens. But it's extremely frustrating!
5) Music didn't seem to end in Plagal Cadence (or is that just my ears).
I'm honestly not too sure what that means. If you mean it ends too abruptly, I agree. It will be fixed.