After trying to use my own composer.json file for development. I fell back to the deps file. I fell in the trap of removing the vendor and I had to spend two full evenings to get to a proper config set on up to date and working bundles.
Enjoy
My current Symfony 2.0.x (favourites) vendor dependencies
This is my current, as of July 2012, favourite development environnement configuration files, use it if you want. This is mostly for me when I switch computers.