My OG Droid used to pair up no questions asked after I turned the head unit on. Not so much with my Galaxy Nexus. After reading around for a while and fighting with it (hitting the connect button 3-4 times to get it to connect... random disconnects.. etc), I found a result from google that suggested pairing it from your steering wheel controls as opposed to the head unit.
..I'll be darned if it didn't work. Had to go through the voice prompts by first clearing out my phone from memory and then hitting the phone off the hook button etc... But darn, it syncs right up now once the head unit is on.
Whatever. Not going to ask questions. Just wanted to post up here in case other people were having this frustrating issue.