good, but not necessarily intuitive
first off, i really liked this. as might be evidenced by my having played it for the last 7 hours straight. the strategy involved with the changing roads is good, and those damn hero seeking flying mobs are a pain, but fun to try and thwart.
i noticed someone said they couldn't find where to spend their points. this is valid, since i only found that menu on accident. to anyone reading, it's on the right of the main map screen. click that thing and a menu for skills pops out.
someone else said there was no way to plan for the created roads. this isn't true. the game highlights unpaved roads in red on the maps. you can tell exactly where they are going to occur.
i really did like this game. especially that upgrading towers completely changes how they play. for instance, early in the game, earth2 towers are about the best thing you can have, combined with ice towers.