The reserve TPU button has been available on the dashboard for the last few months. But I assume instances have been prioritized for large customers such as Two Sigma.
From the paper:
"Despite low utilization for some applications, the TPU is on average about 15X - 30X faster than its contemporary GPU or CPU, with TOPS/Watt about 30X - 80X higher. Moreover, using the GPU's GDDR5 memory in the TPU would triple achieved TOPS and raise TOPS/Watt to nearly 70X the GPU and 200X the CPU."
In-Datacenter Performance Analysis of a Tensor Processing Unit
From the paper:
"Despite low utilization for some applications, the TPU is on average about 15X - 30X faster than its contemporary GPU or CPU, with TOPS/Watt about 30X - 80X higher. Moreover, using the GPU's GDDR5 memory in the TPU would triple achieved TOPS and raise TOPS/Watt to nearly 70X the GPU and 200X the CPU."
In-Datacenter Performance Analysis of a Tensor Processing Unit
https://arxiv.org/abs/1704.04760
Price is about 5x cloud nvidia gpu instance on an hourly basis.