Many people have asked me what do I think was the best thing about Percona Live UK. I always answered: that it happened in the first place! This was the first time we had such a large and high-quality MySQL conference in Europe, and many well known bloggers and speakers that can't always travel to Santa Clara were present.
More importantly, many MySQL users who don't travel to Santa Clara could now see them speak and meet with them. I met at least 4 hard core MySQL DBA's from Helsinki that I've never met before. We had to travel to London to meet each other! (But if you are in Helsinki, we have our first MySQL user group tomorrow, this should fix things!)
When I walked into the conference venue, I introduced myself to a person that stood there talking to Baron Schwartz. He introduced himself as Schlomi Noach. Then we started laughing: we know each other quite well, Schlomi and I run the annual MySQL awards as co-secretaries. I never realized we had not met in person before!
The content of the program was very high quality. In the past few years I've come to value informal one-to-one discussions as my primary source of new information instead of the official lectures, but at this conference I actually chose to attend as many talks as possible and learned new information from many of them.