To update a prior post of mine... it seems your sight radius increases about every 200 skill in Observation. Also, once you get to 200 Observation, don't forget to run through the Sewers and the Dungeon of Mystery 1st Floor again, hugging the walls. Even though you won't see anything change, you're still scouting, so you'll get some skill-ups.
It's been a long time since I've seen a new Tower Defense that I thought was pretty decent. Now I wonder how long it will be until it happens again.
Kudos!
My only complaint is that when the camera changes, you start running in the direction in relationship to the camera, and not in the direction you were already going.
Just a minor thing, but could we get the Archery skill listed closer to the rest of the attack skills? It seems out of place being second-to-last in the list.