I've been playing Zelda II a bit over the past couple days. I haven't even beaten the first palace, but I've found a heart and magic jar, then decided to go learn Life before beating the first palace, wondering why I never thought of that before. Mostly what I've found is that the 3DS's controls make the game much harder than it ever was before.
When I played this on my GameCube, I found the analog stick really good for the game. That was the first time that I ever looked forward to fighting blue Ironknuckles, since it made me feel like such a bamf blocking all their attacks effortlessly while I cut them down. On the 3DS, I was nearly killed by some bits and a Stalfos. A Stalfos can't even attack low! There is no challenge to blocking them, or at least there's not supposed to be. There seems to be something about where the circle pad's thresholds between left/right and up/down are that I just can't feel out instinctively. It's really obvious on the world map when I start walking back and forth left and right when I'm trying to move down. The D-pad is more accurate, but it's not even remotely comfortable to use.
The power button hasn't been a problem yet, and I really like having Y act as select, although that makes me wonder why X can't be start.