the breakdown at 0:40 didn't sound in key for me, but that's just my ears. i understand this is an ambient track though so i forgive that =)
you've got some nice sounds going on and i like your melodies. everything was on tempo and intact so for ambience i'd say it's soild, but i wish you'd pick a key. but it doesn't matter in this genre. so great work with your melodies and dreamy synths.
keep it up!