I had a fantastic time, yesterday 14th and today 15th of November, at CodeKen London 2011.
This was (superbly) organized by +Jon Dickinson, and sponsored by Equal Experts (http://www.equalexperts.com/).
I had the pleasure to meet many SO users, including +Pekka Nikolaus (really glad you were able to come and enjoy this event), +Stefan Plattner and many others.

That event was, however, remarkably not supported (as perceived from the outside) by Stack Overflow, even though all the speakers and the vast majority of the attendees were SO members.
The latest SO podcast (http://blog.stackoverflow.com/2011/11/se-podcast-26/, at 15'43'') was a bit mysterious to many of us: "no news for DevDays"?, while the replacement for the original DevDays London was about to take place a few days later, at the same dates, in the same neighborhood, with almost the same speakers...

Regarding the presentations, I was impressed by the pragmatic approach of +Sean Reilly in his "Well RESTed" talk.

+Jon Skeet "got evil", of course, during his presentation, with the help of not one, but two socket puppets. Very entertaining as well as informative.

The presentation that really blew my mind was "A Beginner's Guide To Hardcore Concurrency", presenting what Michael BARKER (http://stackoverflow.com/users/6365/michael-barker, http://mikes-tech.blogspot.com/) and Martin THOMPSON (http://mechanical-sympathy.blogspot.com/) had learned when making Disruptor (a Concurrent Programming Framework: http://code.google.com/p/disruptor/).
The quote from Henry Peteroski on Martin's blog (http://mechanical-sympathy.blogspot.com/2011/07/why-mechanical-sympathy.html) summarizes it all:

"The most amazing achievement of the computer software industry is its continuing cancellation of the steady and staggering gains made by the computer hardware industry."

The impact that their approach has on the business model is well illustrated in +Martin Fowler's article: http://martinfowler.com/articles/lmax.html.

As for myself, I managed to gave my presentation (http://www.slideshare.net/dchaffiol/dvcs-in-big-corporation) despite some demo issues ;)
The questions were mainly around why using DVCS (rather than simpler centralized VCS like SVN).

But the main feeling I will keep from my conversations with my SO peers is illustrated by the expression (http://www.reddit.com/r/LifeProTips/comments/fvk27/if_you_are_the_smartest_person_in_the_room_you/, not sure about the author)

"If you are the smartest person in the room, then you are in the wrong room."

Let's just say... I was most certainly in the right room.
Shared publiclyView activity