The other thing that is missing in this convo is the fact that the software is upgradable. I remember our 08 335i had the old style navi, our 09 135i had the new iDrive. We were amazed at how much better the 09 iDrive was compared with the clunky DVD based system. We wanted to upgrade the 335i but it couldn't be done without significant hardware change.
This Dynavin unit is much more flexible and offers a number of features that you simply can't get with the OE navi.
This is not designed to be a replacement for the OE iDrive navi, if you have that, then there is no reason to go with Dynavin. If you have a standard non-Navi headunit, the Dynavin system is light years ahead in terms of features, functionality and of course looks. For a plug and play system, this is about as OE as it gets for aftermarket integration.
I am unbelievably impressed with Dynavin's fit and finish and would not hesitate to put this on my own car as a replacement for the outdated and functionless orange lit headunit.
Certainly there are drawbacks to replacing the OE headunit but the amount gained (navigation, bluetooth, upgradable maps, ipod integration, USB stick integration, touch screen, clean interface) is MORE than worth it IMO. I see no reason why you would not do it given the number of pros.