Just finished this one. No much to say that hasn't been said above, but here are my bullet points:
The dungeons were (with one exception - level 9) very easy. As Nightmare said, this is probably on a part with the second quest in difficulty.
Having to level jump is a serious no-no. I have no problem with sections of a dungeon being inaccessible until finishing a later dungeon, but the triforce piece should be obtainable using only tools from the current and earlier dungeons. So, the stuff in levels 2 and 3 are fine, but the whistle in 6 to finish 5 is not. If I hadn't looked here to see if I had missed something, I might not have even finished the quest, thinking it was broken!
The lanmola problem mentioned above happens if 2 keys are supposed to be present at the same time; If you grab the one being carried by the lanmolas before killing them both off, then you get both keys and everything is fine (I'm pretty certain I got 2 keys from the room).

Dungeon level 9 is where the big problems I have occurred. There are too many rooms with tons of rope-likes. This gets very annoying very fast. As I have said on a few other quests, an interesting challenge is good the first time or two, but not the huge number of times you have to complete (and, often, recomplete) the same rooms. After getting tripped up by various things the 3rd time (in particular coming up a stairway to appear ADJACENT to a rope-like was NOT fun), I started simply hitting retry each time I lost my shield, rather than having to gather yet another 90 rupies to replace it. The dungeon seemed to have complexity for complexities' sake,with large numbers of paths leading to the entrance again. Since getting caught by rope-likes is effectively a restart (with all the wizrobes, I wouldn't recommend continuing without a magic shield, and if you leave the dungeon, of course, all the monsters reset), this caused the level to have a very high frustration factor for me. Getting trapped in room 50 didn't help this any.

Anyway, there were some high points as well in the map. The clues for some hidden items were well done, and though small, the dungeons were generally well done. It was just a little too easy for a 5th quest.
My overall rating is still a very respectable 3.42 out of 5.