Intelligent items are basically a persistent NPC dialogue source which allows the DM to have a verbal say without having a DMPC. That's a solid reason to have them right there.
Cursed items show that magic isn't just about making sure you have the right hit and damage bonus appropriate for you level. It's about magic being about more than just buffing and system bonuses.
Strongholds are about goals. Having plans and goals larger than the current quest or dungeon delve or whatever. They also can represent a departure from railroady play and more towards sandbox play as you tend to the area you are building your little empire in.
In short, all these things are awesome.
Not at all what I thought of when I voted for them, but I do like the thought.
For me its more about:
Cursed items and Intelligent items - allowing greater range of what makes magic items magical. And allowing the simple assumptions which permiated the previous couple editions to go away. If any item can be sentient, with its own will and goals then it adds a new level of awesome. It is like when that goblin surrenders and gives the reason for his hideous acts. The same goes for cursed items but in a different way, the party must be cautious about items they get instead of just assuming every weapon is a +2 sword of kickass they have to be weary that perhaps that item came to them because its previous master was unlucky enough to get it killed in the first place.
It isn't even like I use intelligent or cursed items very often but I certainly want to see their existence at some point coming up in 5th. They are just too cool to pass up. If I want to have use the items as plot related objects, like I would use certain NPCs, then I want to have rules related to them. I loved the idea behind the swords in the book of nine swords. I didn't like the execution, but the idea was brilliant. Giving a unique and personal twist for weapons, or armor or wondrous items or staffs or anything, adds a new layer of cool and complexity that I don't get if every item is just what it seems like and never changes.
As far as strongolds, I probably voted for this one differently than I suspect most did. I voted for strongholds for the party, not for the fighter

I've used strongholds a couple of times in games and they really allowed for interesting and unique scenarios but I think they have been solely underused, especially at lower levels. I love the idea of the party hanging up their shingle and able to be found in just one place. I love the idea of giving them resources to protect or a PLACE to care about instead of just NPCs. I love the idea of NPCs coming and establishing a town around the stronghold, with the party being heroes strong and capable enough of protecting the little outpost in the middle of nowhere.
However, I think that strongholds don't really have very good rules attached to them to achieve such things that I want to do with them. That is why I voted, to see rules be created to allow me to drop such a thing into a campaign for my players to use. That would be glorious.