They're definitely worth taking the time to watch, imho. I've gone through most of them over the past couple of weeks, and have just a handful more to watch (and will probably skip Kurzweill and the econ/vc ones). My favorites so far have been Schmidhuber, Hutter, Drescher, and Nielsen (Quantum Computing). Anna Saloman's talks were both very good as well, as was Eliezer's if you haven't heard his existential risk and cognitive biases lecture many times before.