In the final few episodes, the writers were just throwing things against the wall to see what would stick, including trying a totally out-of-the-blue romance between Maggie and Chris. Ultimately, the ratings got so bad that the show was canceled. It did have a series finale that, for the most part, felt like just another episode until the final scenes, over which the song "Our Town" (which, thankfully, Universal paid for the rights to) put a bow on the series.
The DVD set is a five-disc set. If you get the US DVD set, the only extras are deleted scenes for most of the episodes. Of course, the issue with the music in the US releases remains, with some, but not all, of the original songs from the show being replaced with canned instrumental music. As I said above, thankfully, the final song to appear in the show, Our Town, was used because the ending montage would not have worked nearly as well without it.
Overall, the final season was uneven, to say the least. The show definitely lost a lot with Rob Morrow's departure, and without him, the show could not have recaptured the fish-out-of-water aspect that made the show so good in the beginning. Unlike the show ER, which survived multiple cast members leaving and could plug new characters in for those who left, I equate Morrow's leaving akin to what would have happened if Alan Alda had left MASH. He was clearly the main character, and the show could not survive without him even though the other actors did a great job in their roles. Unfortunately, the show just petered out at the end and never got a great send-off.