That's a really cool picture. In terms of stitching, though, it's really, really easy, because of all the reference points. Try stitching sky. :-p
Depends on how the photo was taken.
If it was taken from a camera carefully mounted on a special tripod where the rotational center was at the camera's focal plane, then yes, stitching is a doddle.
But if it's from handheld photos (and the photographer isn't careful to rotate around the camera's focal plane), a set of complex 3D objects like that makes you run into the issue of the parralax changing, making various bits overlap differently from tile to tile. It's worse, even, than the situation where you do large outdoor panoramas and someone is walking across from tile to tile.
In fact, looking at the photo more closely, I see some blurry bits that look like just that situation happening.
You can work around this by exporting your auto-tiled image as a Photoshop file, and painstakingly editing the layer masks so that the misaligned objects don't appear doubled or blurred. I rarely have the patience to do that.