It was fun. I was *really* impressed by how well the event had been scaled up from last year - whilst I'm sure there were glitches which other folks noticed (Wi-fi problems, say), I thought it all ran extremely smoothly and felt very professional.
There was a limited backchannel, considering the number of Wi-fid folks there in the audience. I think an AJAX chatroom was intended as part of the dConstruct backnetwork, but it never materialised in time. In the morning 6-8 of us hopped into IRC but it could've been a lot better.
I unfortunately only managed to attend the morning talks - I hopped back to FPHQ at lunchtime and became embroiled in debugging a problem reported with a service we run, which kept me at the office until the end of the day and stopped me attending the afternoon sessions. (As an aside, it's an icky one too: 2 identical Hibernate-backed applications returning different results from the same dataset on different machines).
Of the morning sessions, it was Jeff Barr of Amazon who blew me away: the Amazon S3 and EC2 services look incredible (though they're not for everyone, I suspect). There are a couple of things we are looking to do at the moment for which EC2 might be perfect (and wind up saving us tens to hundreds of thousands of pounds). More here when I've had a chance to look into it, but the pay-as-you-go nature of EC2s computing power knocks aside a few assumptions which we tend to have when designing large-scale systems.
Simon and Paul of Yahoo were characteristically enthusiastic, and it was good to learn more about the Yahoo APIs, but to be honest I was already sold on the idea of APIs (as I suspect many of the audience were). Exposed by web services or not, IMHO clean APIs are a consequence of good software design, so I don't see them as anything magical... and applying the term "mashup" to internal software projects strikes me as a little bandwagonesque. When does a new product which ties together data from existing services stop being an application and start being a mashup? It's all angels on pinheads stuff, I suspect.
Jeremy gave an extremely engaging talk; I'd heard he was good but hadn't seen him work a large audience before, and I was very impressed. A very personal and personable talk; though again, I was already convinced that APIs are a Good Thing so didn't have any "aha" moments.
In the evening I popped down to The Terraces and caught up with a few familiar faces. I was knacked so didn't stick around long, but it looked like a good do. Kudos to the ClearLeft guys for organising all this and doing such a good job of it - it's fantastic to see so many folks gathered in our little seaside resort :)