It's OK
It was enjoyable at first and kept me playing until the end, but the more you played, the more problems were noticeable with the game.
1. The "perfect score" makes no sense since you just get a high score by playing one level for ages and killing people off with your crossbow rather than sending lots of troops to destroy the castle. The only limit to your score on any level is boredom. A better idea would be to have the "perfect score" as a maximum score and to only award all of the experience points gained if you get less than that score.
2. I was halfway through the game before I realised that I could just hold down the keys to fire a constant barrage of arrows. You should have an autofire option or something - perhaps have auto-fire on by clicking the icon on the screen and then off by clicking again or by hitting the relevant shortcut key.
3. The crossbow is way too powerful. When it was fully maxed out I could keep the enemies even on the final level at bay pretty much permanently while I built up my mana reserves before unleashing an army of troops. Hint for playing the game: max out the ordinary crossbow early.
4. The game is way too easy except for the final boss who is way too hard and too long - it's just a game of attrition against him and so dull.
For those who can't defeat the final boss, the tactic that worked for me was to just fire arrows constantly and send out alternate dragons/angels with an undercurrent of hobbits. The hobbits are no good for fighting but they slow down the movement of the boss when your angels and dragons get killed. You win with the boss by slowing him down for as long as possible. It's stupid, but that's the only way it seems to work.
5. The game really needs a fastforward mode.