I don't know why you have such a hard time accepting that the game can be thoroughly played in a good eight to ten hours
I guess it's just because the above can easily take 3-4 hours by itself, and it's hardly half the game? Hey, I can't doubt you - you say you did it all of it in about an hour or so, I have to take your word for it, but personally I'm on my second time through - been playing for about 2 hours+ on and off, and I'm still far from done in Seattle.
I definately agree that it's not as large as DX1, but I found it to share much of the plot concepts, stories and feel of the first, and in some ways more interesting than the first. DX1 felt like the whole world had been taken over by a warehouse, whereas DX2 has pop singers and coffeeshops to deal with. I certainly regret the lack of a skill system, but I still found it necessary to think through scenarios like in DX1 (well, until the end when I'm basically an uber-cyborg ... but then again, that was true in DX1 as well).
Certainly, each to his own. I too would have preferred a more complicated DX sequel, but I just don't deny the heritage either.