Speaking from a GM's perspective, what I see as interesting in 4E are actually not individual powers, classes, characters or whatever, but how they combine and mix to form "more than the sum of the parts"..
Heh - this reminds me of a nice scene we had while the PCs were in the Feywild. They were attacked by enemies on flying steeds while they were peacefully wandering and shopping in the square of a small Fey town. Realising that every inhabitant of the town had either the ability to fly, teleportation or invisibility in some form, and giving all the "innocent bystanders" the same initiative pip, I arranged it that that one moment the square was a bustling marketplace full of exotic fey folk, the next it was empty of all but the PCs and their foes. Every inhabitant either flew to an upstairs window, teleported into a house through a window or went invisible and left the square. This simple (and systemically natural) development said "you are in a fey settlement" more graphically than any of my whimsical description did!The most interesting single power in D&D4 was, for me, the Fey Step.
Not because of its tactical uses (although it had many), but because of its world-building potential. It significantly changed how the whole race interacted with the world and it was a great fun to explore in play.
In general, I love the places where the system and fiction build on each other.

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