D&D 4E Good adventure that shows 4E's strengths?

[MwaO]

While I'm biased, I think the NETH4-1/4-2/4-3 series from LFR make a solid set of mods showing off 4e's possibilities and strengths. I'm the co-writer of NETH4-1. They're available(and most of the other mods from LFR) at http://www.livingforgottenrealms.com

 

[pemerton]

I have said it from very early on, the 3e module "Speaker of Dreams" works real well. It'd require conversion, but it naturally has that "delve" format going.

I used bits of Speaker of Dreams - mostly the cultists. (In my version, the baron wasn't taken over by a mind flayer but rather stalked by a catoblepas.)

For the cultists, I used a doomsayer and some similar NPCs from the Demogorgon/Dagon entry in MM2, plus the human hexer. Plus the "half-demon" (I can't remember the proper name) and the guardian demon from Demonomicon.