What about Torch or Theano which allow you to use multiple GPUs and clusters? they also have a wide array of libraries which allows you to extend capabilities (itorch etc.). torch is also very fast, most parts written in C so I don't know if Tensorflow would be really that fast compared to existing librairies.

One thing find I found interesting is the ability to use the software you designed in research directly in production (without having to rewrite the whole thing in java)

That said, I'm excited to see Google release this. Hopefully it would encourage Facebook or Baidu to also release