My group has been running the 4e version of the Zeitgeist adventure for close to 2 years, and we're now on Adventure 9. It is, far and away, the best adventure I've ever run. The NPCs, the setting, the storytelling ... all of it just bleeds flavor and has completely absorbed my group.
If you love D&D 4e - as I do - this is the adventure which finally makes the playstyle "click." Forget about the awful slogs that WotC has produced; Ryan understands how a proper 4e adventure should flow, and the right mix of combat and non-combat, to make the system really sing.
You may need to tweak some of the enemies along the way depending on your group, but the monster design herein is as strong as any I've seen in any official product. It's phenomenal.
[5 of 5 Stars!]