As a few people have posted, I too have noticed that after the Nav upgrade the stored destinations directory now takes a while to load after first starting the car. I might have found a workaround:

1) Press the Nav button
2) Go directly to the Nav display by pressing the Map option and wait for the map to display.
3) Press return
4) Press the memory option
5) The "Load" menu items should turn blue almost immediately.

I have found that this seems to speed the loading of the stored destinations. As a geek, I have a guess as to why, having worked with both QNX (the OS that powers the MMI) and Oracle (the embedded database NavTech requires):

Both the Nav database as well as the stored destinations are (probably) powered by the same embedded Oracle database engine. The database engine is probably started by the first task that requests its services and inherits the task priority assigned by the programmer. Assuming that the Nav Map update has a higher task priority (since it needs to process near-real-time data) than the Stored Destination Load, going to the Nav display forces the Oracle database engine to start up faster.

Or maybe I'm just full of crap which is an equally likely answer.

I have an old Navi Plus type C in my D2, which can be slow sometimes to start up or to calculate a route.

I notice that if I input a destination, then as it is calculating I put the map view up, it takes forever. This is due to it using its computer power to refresh the screen shot continuously.

If I take it off the map display, it calculates the route very quickly.

Is there degradation of any MMI functions with the NAV upgrade other than those that directly effect the NAV? The DVD I currently have is W531257002, Version 2 (that came with my '05 in July) and I think that W531257002A, Version 4 is the latest.

I doubt very much that thi is using user based priroties for two reasons:

1. I would expect a single run-time user is in use.
2. This is a real-time implmentation and priroties willbe set based on response time requirments not on a user based priority scheme.