It's November 2009 and you're buying a '09 'vert... beat them to death on the pricing!
I got my brand new '09 E90 335i back in October when there were tons of rebates. Deal was too good to pass on... $10k off MSRP!. I know that sedans are generally cheaper, but this really shows dealers are highly motivated to 'give away' those remaining '09s on the lot.
Seems like November rebates aren't as good as last month. If I were you I would probably offer $2500 under invoice, minus the Auto credit ($1260), and use BMW financing to get the Holiday credit ($1500?) but pay it off immediately. Dealer may screw you on the trade-in, though.