I played the demo. As far as tower defense games go, it's good.
Though, very minor; I'd suggest organizing the intermediate menu that allow's one to return to the main start screen or go to the main game play. It wasn't obvious what button to select to play. Despite figuring it out it caught me off guard a bit. I didn't have a problem connecting with 'Return' symbol but on the other hand I thought that the picture to the main play was apart of the scenery. Perhaps, at your discretion set that particular menu a bit centered. Maybe, with 'Start' or 'Return' embedded into the actual icons.
The main game is fun and eazy to get into(at least from the demo's aspect). I think the bounding or collision boxes could be more in tune with the tower's mound. Though, it's not a big deal in the demo but might give the final game version a polished end. The sound and music fit the game well and moved the game right along.
Overall, I enjoyed the demo and look forward to getting the actual game, despite the minors I mentioned.
BTW, did you do all the graphics and music yourself?