I only played it in the 3d version, but i thought it was pretty easy. Maybe a little boring, but easy. I think i had a harder time with the fire temple.
The original version is a bit harder because it lacks the colored lines leading you where you need to go. It is more annoying because the interface involved with putting on and removing the iron boots was not as smooth. You had to pause and equip or unequip them constantly.
However, even on the original, I didn't think it was that bad. The only annoying thing is that there were some keys on one level which you had to access through doors on a different level, so it is not always easy to track which ones you should have gotten at each water level. If you aren't familiar with it, it is easy to get to the end and realize you are a key short, but you aren't sure where you missed it.
Whatever annoyance this was, the the coolness of changing the water level and the Dark Link encounter made this a great dungeon.