Not quite, I think? That page suggests that you can only use versions in this manifest: http://heroku-buildpack-nodejs.s3.amazonaws.com/manifest.nod...
...which doesn't list 0.8.
...which doesn't list 0.8.
Just make sure you specify the latest npm as well. http://heroku-buildpack-nodejs.s3.amazonaws.com/manifest.npm
Upgraded my app to node 0.8.0 and npm 1.1.9 and seems to be working okay.