It was actually quite easy during my first playthrough. I was preforming somewhat of a
rushed minimalist run, as I could only play over the weekend (a story for another time). Once I got into the flow of things, everything went rather smoothly. I got hung up on the part where Zelda gives Link the sailcloth, but that's about it as far as the beginning of the game goes.
Basic enemies can be easily dispatched if you catch on to their attack 'patterns.' This is especially true for Bokoblins. I admit, however, that the Lizalfos' speed overwhelmed me...and still does
[noparse]
[/noparse]. Later in the game, upgraded versions of many enemies began to appear - not only in new places, but in areas that must be backtracked - I had to change my MO a bit, but they stuck to the same attack patterns for the most part. I didn't have much difficulty there... To be perfectly honest many of the common enemies could be defeated by simply flailing wildly about
(lol). The enemies in
SS have a wide range of difficulty, as in most Zeldas.
The puzzles were a piece of cake for the most part, but there were moments when I had to pull out the old thinking cap. I'd attribute this to the fact that some of said puzzles were entirely new to the series - given the motion controls involved, so catching a snag once and a while was not unexpected. Those particular puzzles were a lot more time consuming than I'd liked - given my time constraint, I admit. (Sandship door thingy) Overall, the puzzles were easy to moderate.
The game's bosses ranged from easy to hair pulling for me,
but it gets tricky. A good example of this was Koloktos. It had several 'substages' of battle that flowed in repeat. I could almost say it was the first of its kind in a 3D Zelda... (again, a story for another time) I'd say this gave it a difficulty ranging from easy to insanely difficult all in one battle. Ironically, I beat Koloktos with only three hearts remaining for
most of said battle - no potions, no fairies, nada. The game's other bosses were a walk in the park for me, minus The Imprisoned p.2 and neither of them took me more than three tries. As I've stated before,
SS bosses were tricky, as their difficulty sort of 'fluctuated' with each phase of battle.
The above covered enemies, puzzles, and bosses. There are some other components of the game, such as missions (water basin

) and side quest (Fun Fun Island) on which I caught a bit of a snag, but they weren't too bad... Keep in mind, I spent most of my first play without a shield, a wonky Wii remote + and nunchuck, and pressure the from time constraints baring down on my shoulders. Despite this, I beat the game in roughly 50 hours; I have yet to take Hero Mode for a spin.
Overall, in my opinion, I'd say the Skyward Sword's difficulty should roughly range from ridiculously easy to moderate for seasoned veterans, and moderate to hard for newcomers.