The original campaign for Left 4 Dead was pretty rough, lots of spots to jump out of the world/glitch it. Seems to be a direct port (with the addition of l4d2 weapons) however the real main issue is that the finale DOES NOT WORK. That automatically makes the download worthless. Untill that is fixed I wouldn't suggest playing it. Also LOTS of pink/missing textures, probably because it wasn't properly ported over. As I said until the finale is fixed don't bother with this one. Play the original instead :)
Welp...