I found I enjoy the full L4D much more than the demo. The second level of the demo was cut pretty much in half, and the campaigns keep me occupied for about an hour on normal/solo. Of course the best stuff is when you go online with others, so we got a group and played through an advance campaign, which took about 2 hours (we couldn't beat the finale on advanced after 3 tries, had to vote it down to normal :-/). Also, versus mode is amazingly fun, especially when you play as the infected. If you haven't gotten it yet and want to wait, you might find that it goes on sale next weekend, though shopping for anything on black friday is nuts in and of itself.