I took part in the last round of the Good Judgement Project, and finished top 20. I also work in the field (although around more specific incident forecasting than the GJP worked in).

I think the points made in the book (and on the GJP blog[1]) are useful. The idea of trying to put probabilities around your assumptions is pretty useful for example.

The other lesson I learnt was that predicting things to stay the same is generally a safe bet. Often the challenge is working out which side of a prediction require less things to change.

If you are interested in the details, [2] is a pretty good overview.

[1] http://goodjudgment.com/gjp/

[2] http://www.nesta.org.uk/sites/default/files/1502_working_pap...