Birdviews aren't brilliant, not had one but heard many people curse them. they do the job, but they are a bit primitive. they don't do full postcode searchs and the graphics aren't brilliant.
another alternative is
the Pioneer F500BT
see review below
viewtopic.php?f=27&t=33501&hilit=pioneer
gives all the benefits of a Pioneer unit and also full manufacturers warranty and fully legal software with Traffic updates and speedcamera datebase updates.
may not be fully OEM flush fit, but does offer alot of options and comes in at a similiar price as some of the other options out there.
other options also include running somethi g like a tomtom in the cubby or garmin