I played through the game on easy and enjoyed it (mostly).
First, my biggest gripe was unreliable timing at the end of the levels. Sometimes it would take as much as 2 minutes for the game to move on after the last enemy appeared to die.
I would have given this game no less than a 7 if it weren't for the above-mentioned "bug".
Second, another major gripe, was the fact that you could not stack spell effects. For example, you couldn't cast fireball and rapid shot at the same time. I could understand if iceshot and fireshot couldn't mix, but there is no logical reason why rapid shot would be overridden if you also cast summon footman, summon boulder, fireball, split shot, poison shot, etc.
Lastly, but least importantly, I would have liked some of the effects to have been a little more polished. For example, the death beam was rather dull, just a straight black line. Also, there is a bug that causes artwork from the level to remain when the menu pops up for the next level (I.E. I often had my boulder survive and it would appear overtop of the spell buttons in the memorise spell menu), this also happened with projectiles like arrows/iceballs, etc.
Overall, good game. With a little polishing and a little more debugging, easily an 8. Now I'm off to try to beat the game on normal.