If you are really bummed by the switch or how it was handled, I second calling and explaining your disappointment. I'd convey that you were a bit taken off guard by the agent when you received the call and now that you've had adequate time to think about it you aren't pleased about the situation.
Personally, if it happened to me, I wouldn't look at this as a downgrade. I like both BC and BWV equally and they have a similar theme. I think the switch is pretty "fair". Now getting called and saying I'd be going from the Grand Floridian to OKW would be an issue.
Others might disagree, but if you are looking for some sort of compensation I'd think some extra fastpasses or maybe a giftcard to cover dinner would be appropriate. I think for a move <24 hours out that's a fair outcome. Any more i think would be over in excess of the issue.
Either way, enjoy your trip!
Excellent advice.