Thanks for this epic review thread. It gave me the impetus to finally buy some HD 25-1 II's to replace my PXC 300's. I haven't tried them yet on a flight, but they sound great at home. For the first time I can appreciate the different characteristics when I compare them to my Audio Tehnica ATH-A900's as well. Changing headphones is a good way to rediscover your music - stuff you've got tired of with one set of headphones needs to be tried again with a new set.
Anyway, yeah. Thanks. Amazing effort.