Water Temple boss was alright, ice temple boss is the annoying one (awesome background music, though). The water level boss is only a problem in that challenge-thing by the Jolene-reincarnation, as you're pretty much guaranteed to get damaged.
Anyhow, some hints which might help: Keep playing even untll after the screen switches back, take your time, and repeating notes does not seem to be a problem, as long as you don't blow in the orange pipe... That's how my brother did it, at least (if you have a younger brother, ask him).
But yeah, it's not like the LoZ team to leave something like that in, it's truly my only disappointment in the game so far...
On a different note, I had enough treasure to buy the golden engine, but not the dragon one ._. (which is a shame since I now have all the other parts). So I've been blowing away leafs for the past 2 hours, I'm up to 80 Stalfos Skulls (._.), and both my stars and wood hearts are in the 50ies, and yet I still have not collected 25 Demon fossils in total (including the ones I used to the Dragon Lair).
Also, don't buy the cake engine (if you're not going completist), it might sound cool, but it's not all that pretty, and the sound's pretty dumb.
Golden parts don't seem to increase my hearts for some reason, BTW, I have 3 dragon and 1 golden part, yet only have 5 hearts...
Also, what's everyone's highscores on the whip race thing? I have 1:08:54 and I wasn't even trying, it's almost impossible to go below 1:15 for me (I think I once managed to drop and still finish in time), and yet that's all you need for the piece of heart, way too simple. Fun way to get the expensive treasures, though, beating up soldiers might be cheaper, but takes way longer.
Anyhow, back to ruining my lungs by blowing away leaves, only 8 more fossils to go!
EDIT: make that 99 skulls ._.
Wood Hearts are up to 78 as well, and yet I still lack 6 fossils.
Just so everyone knows, the treasures only go up to 99.
EDIT2: Silly me, I only needed 12 fossils...
What a waste of a day :O
(Well, not really, I went from 2000 to 9000+ coins thanks to all the junk I collected, and I still have 30 stars, skulls and hearts left
)