Demo is great. Graphics and gameplay seem much better than the first for me. I was reluctant to purchase it with it only been a year since L4D, but I'm glad I did!
I've been getting terrible a terrible frame rate with the map also. Sometimes it plays well, sometimes it doesn't, so created a local server to see if it was my connection, but had the same issue. All other maps play fine.
Great map though! Very fun to play! :E