Symfony 2.0.4 has just been released.
Stability is getting better with each release as we add new unit tests each time we fix a bug. As a matter of fact, since the 2.0.0 release at the end of July, we have added 59 new tests and more than 180 assertions in our test suite.
If you are starting a new project, you can get the Symfony Standard Edition distribution on the download page.
Then, run the vendors script:
$ ./bin/vendors install
And don't forget to clear your cache:
$ php ./app/console cache:clear