I really, really enjoyed this game. In a sense, it's not much different from a jigsaw puzzle, but the fact that any of the pieces can be adjacent to any other pieces and that it isn't immediately apparent if certain pieces are incompatible adds something unique to the problem space. Starting with a huge mess and gradually determining which pieces have to be in certain locations is amazingly satisfying.
The biggest issues as far as I can tell have to do with player guidance:
The path sections that can't be moved are nearly the same color as the moveable pieces, making it hard to visually track, sometimes making me try to pick up a section that I couldn't, or making me second-guess pieces that had to have been right because I didn't realize which ones were glued in place.
The fact that the pieces have to be manipulated in-place causes a lot of visual noise. Being able to drag around pieces on the side of the main area would allow the player to store them out of the way, or to experiment with their placements without limitations.
Finally, it was at times hard to keep track of which pieces I KNEW were correct, sometimes picking them up by accident even though I would have known not to had I double checked. Some way to lock pieces in place (as well as color-code locked pieces) would have made the process a lot more pleasant.