Agree with your premise, but that's my exact thoughts as to why the Nexus would be more preferred by the average consumer. I think when people see ICS, they'll love it because its full of bells and whistles in its raw form. I think it outdoes sense or blur. And the term "Vanilla" isn't really what it used to be. Agree it may have been boring to people before but this is no longer Android as average Joe users have come to know. So if its mostly about the OS bling factor, will blur or sense outshine ICS? I'm thinking not, even to everyday Android folk. But time will tell.
Not to mention pure ics will run smoother than skinned uis.