We're starting a project right now and we wanted to know what's the best course: use Symfony 2, even though it's not stable and final, or use Symfony1 and upgrade later?
I would recommend to start with Symfony2 : migrating from Symfony 1 to 2 will be very difficult, Symfony2 nearly being a totally different framework.
I have to add that even migrating between minor versions of Symfony 1 can be a real pain.