Agreed, it's probably the best library for 3d graphics in JavaScript. That being said, if you want websites that load fast and perform well on a large number of devices, avoid using ThreeJS unless it's absolutely essential.
I used to use a really great lightweight (5k) library in Flash for simple 3D geometry, polygon shading, etc. (anything simple that could be handled on CPU without uploading anything to GPU; I'm not sure I would attempt to do a full screen terrain with it, but a test would tell). So yeah obviously if you need a couple triangles, look elsewhere than ThreeJS. I'm just saying it's a fantastic library... there's really nothing else equivalent in the ecosystem at this point. It is what Away3D was to Flash, which is a compliment.
