FogCreek seems to be winning the game. So I agree with the sentiment that it was productive debt.
FogBugz definitely used to have a lot of mindshare, but...
The fact that FC managed to come up with a successful (but not necessarily profitable) product idea and spin it off into its own company doesn't really say much about the validity of their decisions on a completely different product.
Nor is it evidence of Fog Creek "winning the game" (whatever that might mean)