One word. HOT!
I have never been in a temperature that hot (it was only in the mid 30's - apparently it was even hotter earlier in the week), I was dressed for the wet London that I left behind earlier that morning. But that didn't stop it from being a fun event.
Chris Chabot did a great talk about Buzz. I then presented my "Web Apps" presentation (http://html5offlinedemo.appspot.com/app.html). The talk centred around the differences between Native Applications and Web Applications, some of the core pillars that we think make for great applications and some of the features of HTML5, CSS3 and some of the other supporting specifications such as WebSockets. If I had more time I would have loved to talk about some of the frameworks that exist to help developers to build great applications. To actually show people how to build really cool applications will take it to another level.
We also saw some of the effects of having CSS3 3d transformations hardware accelerated - hint, if you view the slides in Chrome (without using the acceleration flag) you won't see the really cool 3d IFRAME effect :)
We finished the event pretty late and didn't get too much time to do the Hack-a-thon, but we had a great time just talking to other developers.
I thought BetaHaus was an excellent venue, the food was excellent, the staff were friendly.
I am amazed by how well everyone spoke English, it puts my lack of any form of multilingual ability to shame.