Yeah, the game was really easy. It probably doesn't help that there aren't many enemies to begin with, but the ones that are there don't damage you much. I think the only time I really felt like I was getting beaten was on a few of the floors in the Cave of Ordeals, namely the ones with the Freeze monsters and the ones with the Iron Knuckles. After getting through the Cave and fighting some in Hyrule Castle, Iron Knuckles are a piece of cake now, but those Freeze monsters still really piss me off.
In terms of the auto-shielding, doing that freed up an extra button (which I'm sure helped on the Wii version), and it made the Shield Push move easy and intuitive to pull off, but I do miss being able to control the shield myself. My reason is the opposite from yours though - I found myself getting hit more cause I didn't have full control of my shield. By accidentally performing the Shield Push move I opened myself up a lot.
I second the difficulty setting. Plus it wouldn't be hard to add. I think the only option for people like us to challenge ourselves in TP is to pull a low-heart run. I did this with OoT (only 3 hearts), and it was a pretty good challenge. I haven't tried it with Majora's Mask, but I'm sure it will be harder than OoT. I think the problem with attempting this with Twilight Princess is that you get heart pieces everywhere unexpectedly, esp in dungeons. You never got heart pieces in dungeons before, so unless you know what chests they are in exactly, I'm sure you could accidentally pick up 5 pieces and ruin your run.
On the subject of heart pieces, why the need for 5 to make a heart container? If they only had 4 to make a whole, they may have been able to do without having them be in dungeons. Just more excuses to not have "real" ways to get them, ie by interacting with NPCs, which the world is very void of.