I updated my 2011 528i... Purchased the update from Tischer. It's very easy to do. While I don't have firsthand knowledge of the 2012 maps, I generically think every other year is enough. Compared to the 2011 maps, it looks as though they've done a better job of showing street names in a readable way. I still think the daytime contrast is not good due to the gray background.
2011 528i (ED 6/1/11; USA p/u 7/23/11) Space Grey / Black / Light Wood / Sport Auto / HUD / Packages:Premium & Premium 2 / Sport / Drivers Asst
2006 325xi / Sparkling Graphite / Terra / Walnut/ Steptronic /Premium Package - Nav / Xenons || iPod Adapter | Blacklines