If you get a chance, the book is worth picking up. It's very short, but packed with useful insight.
Personally, OSA is just one way of applying important principles of change (in people and structures): create purpose, provide clear intent, involve people, create boundaries for experimentation. Wrapping these principles up in open space technology is clever.
What I dislike is Dan's railing against the "agile industrial complex" (i.e., the "scaling" companies, big box consultancies, and money-mills like Agile Alliance).
Yes, most thoughtful people I know see the faults of the above. But OSA is also a "sellable" thing that Dan has a financial interest in. To me, it comes off as nuclear advertising and makes OSA no different than the rest. There's an almost cult-like behavior of those committed to OSA, at least, as I've observed.
With that said, I'll repeat how useful open space is for change.