Played this over the last week, absolutely wonderful game, took me about 8 hours but I see myself replaying it at least once. Great retro adventure/shooter style game but with enough dialog and lively characters to create a really strong story as well. It reminds me of Link's Awakening but with much more fluid, exciting gameplay.
I'll definitely be going back through to find more of the hidden items, characters and quests (and boss. and ending. I think.), but I feel like playing the game on Hard will be a real bastard for some of the boss fights. Even on "Medium" I had trouble getting through some of them, namely the "X" shaped tunnel boss, the 'twin' dragons, and definitely the "last boss".
Highly recommended, though if you play on a keyboard I definitely advise remapping the keys, default controls had my left hand aching. If you've got a gamepad/controller, I could see that being a really good fit for it too.