I wasn't happy about this either...I like the default bootanimation. Sorry I don't have a link, but if you search galaxy nexus bootanimation in Google, you'll find a link to the original on RootzWiki. You can flash it and get back to the way it was. This should have been an option.
I installed 15 a couple of days ago and didn't notice the boot animation changing. Maybe I just accidentally had the same crappy boot animation as the one in his kernel??? Ha ha. I installed the old nexus 4 color thing instead of the HD stock animation and was too lazy to change it right away.