There are a few differences with the Region 1.
First of all, the menu screen is quite different. It shows an animated KITT dash. Actually, it is very funny and I really like it.
There are no subtitles (as it was in the Season 3 DVD, which was released in the UK last May).
The promotional/introductory videos of Scent of Roses and Knight Song have been added!!!
Certainly, this is the most startling difference with the Region 1 version. 
The video quality is as good as the Region 1 version (I have the impression that the frame cropping is slightly different in the Region 2 and the video seems a bit larger - I am not sure about it and I will check it again).
The small number of missing sound effects in the first episode (Knight of the Juggernaut) have not been fixed (for instance, at the end of episode when Michael press the red EBS button there is still not sound effect).
The packaging of the DVD Boxset is almost the same. The main difference is the 6-disc single-sided edition.
I have just checked quickly few episodes (mainly I checked the Knight Song and Scent of Roses to see if the promotional videos have been added).
I will probably put further posts as soon as I finish checking all the discs.
