1. I learnt that Retroweaver actually works. Retroweaver tweaks your JDK5 compiled classes to make them work on JDK1.4. The JavaPosse had some doubts about it a while ago, but James Strachan and Geert Bevin love it. I'm thinking that DWR v2 will probably adopt this and drop the support for JDK 1.3. Please shout now if you need us to keep JDK 1.3 support.
2. I learnt that red wine and light blue t-shirts don't mix. Sorry Nathalie.
3. I learnt that OCAML is interesting language to teach your brain new tricks. Bruce Tate was talking Ruby up, as expected, and saying that programmers should learn a new language on a regular basis to keep on their toes. However I spent the flight home chatting to Alan Sexton who convinced me to take a look at OCAML and a better mind stretching exercise.
4. I learnt that a simple "hola" (hello) makes a big difference in Spain. I'm not great at foreign languages - I can get by in French, but only badly. I got an extra legroom seat on the flight home for nothing. It's either because the girl at the check-in was magnetically attracted to my rugged good looks, or because I smiled and said Hola. Anyone that has actually seen my rugged good looks will agree that Hola makes a big difference.
5. I learnt that continuations and closures still confuse lots of people. They are very different. Continuations are when you freeze a thread and serialize the stack to be re-run later. Closures are functions that can be assigned to variables where the functions can refer to variables in the enclosing scope. Nothing to do with each other, but often confused.
6. I learnt that it is a real shame industry and academia doesn't mix more. I can't see much in the Ajax world coming out of academia just because the Ajax world is spinning so fast, but there are some brains there that could certainly teach us a thing or two.
7. I learnt that many top universities still don't teach copyright/patent law as a mandatory part of their courses. This is a huge hole. How can you be a good programmer without knowing the basics of what ideas you can copy from others and when?