HOLY COW was this ever a good episode! FANTASTIC! That was pure West-Wing-at-its-best quality. Man oh man.
The pregnancy issues and the captured soldier, both really great story lines. But man, the proposal, and then the 6-year montage of Matt and Harriet arguing about religion in a very respectful way, THAT was just mind-blowing.
The tough thing for the show, I think, is that there's no way they could do that every week, since there's no way that much drama can happen to that cast all the time. With the West Wing, it was easy and realistic for there to be something big every other show or so.
I suspect Sorkin's idea, though, was that the show could be Sports Night alternating with West Wing (as it were). Which is plenty reasonable to me, anyway, but I guess it didn't work for the public.