According to BMW:

NEW FEATURES INTRODUCED WITH NAVIGATION SOFTWARE V27 (4-1/70)
Only E46 (3 Series), E53 (X5), E83 (X3), E85 (Z4) with DVD Navigation system
Disclaimer screen disappears automatically after 8 second
City/Town names displayed in the map

CORRECTION V27
E83 (X3) and E85 (Z4) with flap display:
Software fix for the flap issues (opening/closing)


NEW FEATURES INTRODUCED WITH NAVIGATION SOFTWARE V28 (4-1/80)
There are no new features relevant for US vehicles on Navigation SW V28.

CORRECTION V28
E83, E85, E86: Software fix for the following Display/Flap issues:
Display turns back on after switching "Monitor off"
Flap opens/closes by itself
Flap doesn't open


NEW FEATURES INTRODUCED WITH NAVIGATION SOFTWARE V29 (4-1/91)
Destination input screen changes.


NEW FEATURES INTRODUCED WITH NAVIGATION SOFTWARE V31 (4-1/100)
No new features

CORRECTION V31
NAVI03 and DVD-Top NAV system improved software for:
Reading Dual Layer DVD
Loading voice files