I was in LaunchBox DC (which has since moved to NC Raleigh/Durham area) it was a very positive experience. The advisors brought in great connections: Steve Case, Tim O'Reilly, various startup CEO's, etc for weekly round table discussions and advice.

The overall outcome was a third of the class ended up either getting acqui-hired or taking additional investment, a third is still bootstrapping, and everyone else scaled things down to a side business or just faded away.