4E changed the focus of the adventures to a series of stringed encounters with a minor amount of fluff to move the party from one to the next. Some adventures had some variation, but most 4E adventures that I've read are entirely focused on the encounter setup. The format of a 4E adventure is a synopsis, some story info and then a series of linked encounters that are far more detailed than the overall plot. Compare the format of The Sunless Citadel, for example, to the Keep at Shadowfell.
Sunless Citadel gives you a map and a vague sense of story that you flesh out, however tenuously. 'Keep' gives you context, but then puts you on a boat between encounters. The adventure starts with a goblin ambush. The players go to town for a hook (if they didn't get it already) and as soon as they leave town? Another goblin ambush. Then a battle outside the goblin lair. Then a battle inside the goblin lair. Every encounter detailed, starting from a Setup section, Tactics and Features of the Area. Sunless Citadel has rooms, Keep on the Shadowfell has 'areas'.
The distinction, at least to me, is that 4E focused much more on each individual combat being a set piece linked by an over-arcing adventure, while 3E had an adventure punctuated by set pieces. They both do roughly the same thing, but the focus was different. The logic of the approach wasn't bad, but it led to many 4E adventures feeling like a carnival ride. Sit in your chair and let the adventure carry you along to the next ghost jumping out at you in the fun house. It left me largely dissatisfied with many of the adventures...they felt more like a justification for the (sometimes very clever or interesting) combats and not an actual adventure, per se, IMHO.