Scarecrow is undoubtedly one of the most effective episodes in all three seasons. Despite its flaws, it stands out as an episode with a creepy feel that episodes up to this point lack.
The one thing I felt, however, is that the villain is so obvious from the get go that Micki and Ryan must have looked back on it and realized they were stupid to miss it. I could just see them slapping their foreheads and going 'duh!'. The actress playing her really hammed it up. Yet the overacting actually made the episode more enjoyable. Jack is absent, so maybe that's why they didn't figure it out earlier.
The scarecrow is a suitably creepy looking artifact. It's a complete blank slate, which makes it all the more creepier. The fact that it seems to be able to teleport is unsettling, if a little contrived.
All in all, it's a solid episode. Spooky, campy, and just plain fun. Keep in mind, though, that the low budget still shows and while this was probably the first standout episode of the series, the show was still finding its way. However, with this one, they were definitely on the right path to hitting the show's stride, which they reached a by the end of the season.