For me it's deploying to mobile, mostly. There's ONNX but it doesn't seem to be terribly mature and it doesn't support some of the common ops, and e.g. FB's own Caffe2 doesn't run it natively. There's also no mature tooling to produce quantized models. TF remains the only real option to do quantization aware training or even easy post-training quantization.
Specifically, my life would be a lot easier if I could save a mobilenet-style model to e.g. ONNX or some other static graph format that does not require model code in order to load weights. I would like then to be able to load this saved model directly into something on Android and iOS that can use GPU and DSP present on the chip, with minimal extra futzing.