You would be hard-pressed to find anyone in the PHP community with as much experience in doing DDD as Marijn. Hearing from him about everything that he has been through is very liberating because it's not all candy and roses. It's a real world story.
This was certainly a 5-star talk for me.
The one tiny tip I have for Marijn is to project his voice a bit more; I was sitting in the back and there where (a few) moments where it was a bit hard to hear what was being said.
Create and honest talk about all the mistakes and the traps.
Agree with Jeroen:
"This should be keynote material and conference organizers pay attention!"
Amazingly honest talk about all the mistakes made and (hard) lessons learned when doing a startup while applying DDD.principles. Traps you should avoid, but do anyway, wrong aggregate roots, wrong bounded contexts and the most important lesson of all: not listening enough to the Domain Experts. His talk gives a real life look behind the scenes of a startup that wants to do everything The Right Way, applying all these new cool technologies, and the traps it causes. His one take away? Always ask yourself, "why am I doing this". This should be keynote material and conference organizers pay attention!