This episode appears not to be popular with fans for whatever reason, but I think it's rather successful. Certainly, it creates plenty of eerie atmosphere, though I think some truly bad things could have occurred besides turning the Enterprise into a jungle. And the story itself is a fascinating concept, one that generates plenty of fuel on its own.
Brent Spiner's ability to play "sinister Data" might have been overplayed at this point, but it's tolerable at this point. At the end, Picard the archaeologist takes over, and the ending is satisfying in some way.
That said, this episode does slow down a little at the end; not sure why, but it feels like the story could have been more dramatic. Maybe a human sacrifice, given how horrible Masaka apparently is?