I don't get why everyone is so deeply disappointed. I think it was just a victim of the hype machine.
The campaign was good in my opinion. The only problems I had are what are already listed:
The length of the game. It was quite short, but I wouldn't say it was terribly short.
The ending. It just felt sudden and incomplete. Like they ended the game in the middle of the story. I wasn't quite sure what I had achieved in the end or whether it had made any difference to the story line in the long run.
The emotional aspect. The beginning bit in the bus was awesome, the way everything was portrayed. However, that was pretty much the limit to the emotional aspect. The pit of bodies could have been way better, the slaughter at the house could have been way more involving and overall it wasn't very emotional. This is the bit that disappointed me because I was really looking forward to the emotional concept.
However, with all of that being said I don't think it was any worse than any other FPS out there, sure it wasn't any better either but people seem to be giving this game a fairly hard time when MW2 was just as short, less involving emotionally, and less enjoyable yet everyone seems to rave about it and it's sold the most copies in the history of gaming.
Oh yeah, I was also very happy with the game graphically but the fire in Tiger Direct looked like crap.