Well, let me list and explain some bad points of the pack. And what about the stock yard with laser-trip mine traps. All the crates are explosive, and if you touch one trip mine, the whole place flares white. The different types of security guards, scientists, and zombies. Otis is funny, but you see the original security guards in about 2 places.
Scientists are pretty much the same.
Headcrabbed security guards and grunts show up in only about two places as well. The new alien race. Ok, so they're supposed to be a new race. For all you know they could be different species of the Xen race. They just suddenly disappear for unknown reasons.