I went to Worldcon for one day - Saturday - so this will be a snapshot.
The last Worldcon I visited was Intervention at Glasgow in 2005, when I attended the entire con. LonCon3 was very different. The venue, the ExCel in London's Docklands, was so vast you could have fitted several aircraft hangers inside. It felt like a giant greenhouse and when the sun shone it was boiling.
There were some 4000 attendees at the convention, and it had that inimitable fannish atmosphere that one can come to love. Most visible were the people in Hall costumes, many of them being photographed for charity. And there was a definite preponderance of people with spectacles (like me). There were gamers, geeks, nerds, fans, writers, readers, cosplayers - and even journalists! There were also one or two ball-jointed doll collectors, though I think we were a small sub-set. But we were there too.
The con is diverse, with people from all over the world. Other cities and countries make bits to hold a future Worldcon, as at the Olympics. There was a Chinese stall, and one from Japan. And the atmosphere was fizzing.
We were there with friends Alice and Paul. Alice is a lifelong Whovian, and Paul is a fan of Dungeons and Dragons. The other person was Stephen, my husband, who gamely agreed to accompany me.
We spent a lot of time trotting Hobbit-like from one place to another, occasionally becoming disoriented. We got to visit the Fan Village (a lot), prospect for food from one of the eateries on the main concourse, and plunge into the dealer room, where I kept asking dealers for the rather limited edition of Skeletons in the Closet by William I. I. Read (an M. R. James fan-fic). I saw some very scrumptious second-hand books, and had to be dragged away by force majeure.
In terms of programme events, three of the ones we wanted to see were on simultaneously. In the end, we opted to attend the panel on Adult Readers Within the YA Market with Joshua Bilmes of the Jabberwocky Literary Agency as moderator, together with Ben Jeapes, Sarah Ash and Bella Pagan, Senior Commissioning Editor at Tor. This was partly because I was interested in the panel and partly because Sarah is my sister. (We all went for tea afterwards!)
The panel discussed whether books - young adult, new adult or children's - should be targeted at such a specific audience, and about the fact that increasingly adults are not ashamed to read Young Adult or Children's Books - the most salient examples being Harry Potter and the trilogy His Dark Materials. It was very interesting to me as a person who has continued to read YA books, but also as a writer whose first book at least seems to have appealed to a YA market, though published for adult readers.
The other event we managed to visit was my friend David Wake launching his fourth book, The Derring-do Club and the Year of the Chrononauts, for which I had been one of the proof-readers. We kind of missed the launch, but managed to track down David, his girlfriend and the books. (We made off with a few copies. Having paid, of course).
Apart from that, I had a lot of fun taking photos of a very cool Jedi knight, and Alice got an Imperial Storm-Trooper to pose with her BJD doll, Victoria. (Victoria also got her photo taken sitting on the Iron Throne!).
There have been lots of serious (and some very good) posts about issues like gender and diversity at the Con. I feel that is really important, and I was sorry to hear stories of attendees being rude to members of staff at the ExCel - that really sucks big time. There has been an article complaining that this Con was dominated by old, white men - that was not my experience. Of course, the Con is absolutely huge, but I got the impression that the con-runners had worked overtime to try and make sure that attendees were comfortable, and had somewhere to go if there were difficulties.
I've never attended a Con outside the UK - I would love to do so, but the cost may be prohibitive. I wonder whether there were other indie authors there - I'm sure there were. Perhaps in future it would be interesting to have a stream - or a panel - for indie authors, as there is undoubtedly an overlap with fan-fiction - and trad published authors too. In fact, there's probably a Venn Diagram since there are a lot of writers like myself who have brought out their backlist as eBooks and self-published other or new works.