Great song
you did a great job intertwining all the melodies
(is intertwining a word?)
Over all the song was great, my only piece of advice, not that i am an expert, however when the base comes in at 4:20-4:21 it seems much to loud and clashes a great deal with the very calm acoustic nature of the piece.
if there was any way to maybe blend that in or choose a less powerfull base then you might try that... i don't know, just experiment a bit and see what happens,
In conclusion (now that i have written a small essay :P)
the piece was great and you should definitely be proud of it.
-IMS