I've yet to complete Phantom Hourglass, I'm trying to get through it before playing Spirit Tracks, even though I know PH's is barely a blip on the timeline or mythology... still, best for continuity, the adult timeline is the only one i'll have played in order haha.
As for the difficulty in Ph.. its a pain as far as the timed Ocen King Temple goes, i hate that thing, i had heard bad things about it and thought there was no way it could be that bad, but it is... i can't deal with time and you need to be fast and almost perfect and ugh... i'm on my third visit there now and the swift phantoms have just shown up, and the worst of it is that i know i'll have to return there after this visit and i don't want to so the compulsion i have to complete it is almost non-existent yet i want to play ST because i want the story and don't mind the control system (though it took me forever to get used to)
The dungeons in PH hurt me, i've NEVER played a Zelda game where the dungeons were this easy, i walk in and ten minutes later im fighting a boss and realising it isn't a mid level boss but THE boss, the puzzles are so easy to figure out and easy to to physically solve, nothing slows me down and its over before i know it. PH limps between dungeons, the islands have no heart and it feels like a random jumble of events and a trek through the Ocean King temple beofr another easy dungeon, however i do like the characters and it hurts my heart that PH wasnt a home console game with more challenge to it, i'dve loved to have seen this as a sequel to WW on the Cube or Wii, i'd rather have had SS on the 3DS and Ph on the wii... but...
Another thing i really find difficult in PH is the salvaging arm, i have t constantly repair it becuase it keep breaking it, yet when it comes to using it i dont feel as if the touch controls are as responsive as the rest of the game is... maybe its just me though..
difficulty -3/10 if i don't include the ocean king. 12/10 if i do.