Just to clear things up, the upgrade is technically for 2009 maps and the firmware upgrade is just an included bonus. Also, based on what i have been reading on the forums, the update will have an introductory price of around $70.
IMO, i would get the f90bt. It comes with the ipod cable, larger screen, voice controls, and a 2 year warranty. Even with the upgrade, it should come out to $670.