I had my first MOOC experience in Sep. 2008. It was the CCK08 by George Siemens and Stephen Downes, considered to be the first true MOOC. I wasn't able to keep up with the message flow and felt I was losing a lot, so I gave up a couple of weeks later. I tried CCK09 the following year, but the same happened. At that point I gave up on MOOCs till this year.
MoodleMOOC on WizIQ, moderated by Nellie Deutsch, took place last June. Although I learned a lot about the new Moodle version 2.5 - much more user-friendly than previous versions I'd used -, I still have a lot to learn and much more to practice.
The ELTT MOOC, moderated by Jason R. Levine, took place in August. I learned new things about teaching vocabulary.
The Digital Tools for the K-12 Educator MOOC started in October and lasted for 5 weeks. I heard about and explored several different tools that will be relevant for my teacher training workshops.
I've become a fan of MOOCs that are targeted at a specific area or at specific tools rather than a more general MOOC, as was the case of the CCKs. I didn't notice there were 2,000+ participants in each of these MOOCs. I tended to see more or less the same names in the forums, which leads me to think that there is a high percentage of lurkers. I have nothing against lurking. On the contrary, I believe lurkers learn at their own pace and take advantage of workshops or MOOCs, though they aren't visible. This has been my experience over a ten-year period of coordinating and moderating the BaW workshop.