Except automatically deciding what buildpack to use, what does it offer more to have official buildpack ?

I mean, when you know about Heroku's buildpacks you have access to all of Heroku raw power.

Buildpacks are definitely worth understanding to get the most out of Heroku, but not having official support is a negative. Also, I can't recall what it was but I did check into the community buildpack and it seemed like more effort than it's worth.

That said, I didn't take a very close look so maybe it was easier than I anticipated!