I'm not a fan of mechanical advantages countered by roleplaying disadvantages, which seem to be at the core of the system.
I don't think we can take for granted that there will be no mechanics associated with these side effects of attunement.they've removed game mechanics from the so-called interesting features of magic items and called them "story" features instead. Why have them in the game then, if they are irrelevant to playing the game?
I have the most difficulty with understanding the attunement of magical objects is its limitation in number. Why be limited to three objects, but not four or two? I mean some more powerful magical objects than others should further monopolize more life essence, imho. For example, a dragon orb should count for two or more to compare a climbing ring.
I suspect most magic items won't require attunement. The article talks of powerful ones, and ones that are a significant part of a character's identity - Excalibur for King Arthur would seem like an example. Drizzt is specifically brought up in the article, and has a lot more than three magic items, but it's defensible that the only one that's really significant to him is that Figurine he has. So that's the one he should be attuned to.
I don't think we can take for granted that there will be no mechanics associated with these side effects of attunement.
In the course of 4e design - especially monster design - they have come up with lots of mechanics for giving effect to very interesting curses and limitations within the context of combat encounters. I think they could fairly easily build on that work to develop mechanics that generalise to non-combat contexts as well, and would make the penalties not simply "story/roleplaying" disadvantages.
Mike Mearls said:A magic dwarven axe might compel a character to seek out a lost clan home and destroy the dragon that lairs there. A dagger used to carry out sacrifices to Asmodeus might promise great power in return for fealty to the Lord of the Nine Hells. A suit of armor crafted by duergar might repel all attacks, but freeze its wearer helplessly in place when facing the gray dwarves in battle.
And what happens when the DM says "you feel compelled to head east to the Lost Clan" and the player says "nah, I'm going to resist that temptation and head off south to find that dragon hoard." Does the urge become a compulsion? Are penalties imposed? Does the item de-attune? And what's the timeframe on these effects?

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.