Absolutely stellar campaign despite some hiccups. 5/5 stars.

The atmosphere is superb and the detail is impeccable. I especially love the imagination on display with the fungal growths and whatnot. The Source engine has never looked better! Shame about the FPS drops on Map 1, but oh well.

Gameplay is also nicely balanced, probably thanks to the patches that lowered the difficulty of the initial release. Supplies are more limited than what you see in vanilla L4D2, but it's very manageable apart from the finale.

Design-wise, the finale is actually my only complaint since it feels like a huge difficulty spike. Spawns are still a bit too high (each Tank battle pits you against two Tanks at once, not to mention crazy hordes), and a lack of health items really bites. The game also doesn't tell you rescue has arrived if you're too far away from the door, and I died on my first attempt because of that...

Still, Chernobyl is a must-play!