Apparently everyone is hating on Blackout as a starting talent choice in the shadow spec. Personally I've had a lot of success and enjoyment with it. It feels like it procs more than 10% and it gives me three extra seconds where I can cast a heal on myself, let SW Pain proc once, and let my cool down to bubble again go down 3 seconds without worrying about getting hit.
I don't mean to say that its a good choice for later on but I definitely think its worth picking up when you start to level.