Not as bad as they say, but it definitely has some flaws. Most notably the bugged Faction Wars system, to the point where it's either game-breaking or annoying. Just take my advice and avoid the Stalker-Bandit war entirely. That's the worst of them all, and Bandits aren't nice either. The new artifact hunting mechanism and trading system make it seem much more polished than Shadow of Chernobyl in the "survival" department. Still, it's the most action-oriented out of all 3.
I also loved how the areas were tied together, a few memorable shortcuts being Swamps-Agropom, Agropom-Yantar and Garbage-Red Forest. These add for a lot of new quests and ease of access. I never thought I'd see Agropom so refreshing.
On the other hand, I hated Yantar (the mobile lab, the facility was a wonder to sneak through).
Chernobyl was the most disappointing part of the game. It didn't feel menancing anymore. They hyped it up too much. Maybe it was the pacing?