I think it will be more complicated than Oblivion. But I wonder how enchanting armour will work if you can wear more pieces of armour balance wise.
This could be offset by reducing the strength of the enchantments armor as a whole can be held, for one thing, if you're worried about giving the player more options unbalancing things, then maybe you should rethink game balance so it won't become unbalanced even with more options.
You can see the hair of Mister Conan under his Horned Helmet. Compare this to Morrowind and Oblivion, which replaced the "hair" slots by the helmet, I call it an improvement (it also mean, no ponytail haircut I guess).
I thought it would probably be that when I heard about someone seeming to have the same yellow thing with and without a helmet, as even if you can wear shirts or pants under armor, I doubt you could wear non-armored headgear under helmets, that would be kind of awkward, I think. That's still an improvement regardless, though, because while the whole "helmets replace your hair" thing works for some helmets, fur others, it would just look silly, and other types of unarmored head-gear beyond hoods, like hats and such, which I hope we will see, simply couldn't be done well with helmets replacing hair.
Although in Fallout 3, you could already see your hair even when wearing helmets, so while it's still an improvement, it's one we already saw in a Bethesda game before Skyrim.
But right now, I don't think we have enough screenshots to say how much freedom we'll have with armor slots, because even if screenshots show mix and match armors, it's hard to say if this is actually something done by combining different armor parts, or just the way those armors are set up by default, we'll just have to wait and see. And "Multiple" slots is too vague to tell us much, in short, I'd say we'll have to wait until we get more information before we can say for sure how many armor slots we can expect, though I don't need to wait for information to know what I want, and I can say I'll be dissappointed if the armor slots are simplified further from Oblivion, not to the point where it would stop me from playing the game, but certainly I would not be too happy with the decision.