I'm writing the follow-up on this for VentureBeat. Should be out tomorrow and will answer a lot of these questions. But there are several things I liked about Appsterdam. It's a bottom-up, developer-led movement rather than a top-down, government program. It's about creating a haven for indie developers who want to live in a place that is in line with hacker values and have a life as well as a job.
You are right - it's not necessarily statistically significant. But surveys like this don't have to be in order to give you a feeling for the mood of the community. Also the respondents were recruited from the top Nokia developers (based on downloads) rather than the entire developer population.