Diffcult one. I guess the principle of giving inventors different options is a good development. On the other hand, I worry about the cost differential which might create a barrier to some innovators. I would like to see the extra cost involved gathered from other sources than the inventor (e.g. a levvy on the proceeds from successful patents, national/international fund).
I see one potentially serious issue: if recently submitted "fast track" applications get processed before earlier applications, then there is the potential for earlier prior art to be missed in the review process. While the patent review process has never been a strictly First In / First Out (FIFO) process, this change could make the situation much worse. I'd anticipate the potential for a lot of patent reversals when older applications were processed and revealed that fast tracked patents were actually invalid because of the newly uncovered prior art.
I think this is very bad for independent inventors who already cannot compete with deep pocketed corporations. This actually will make it even more expensive for them if they want to protect their innovations with a patent. A patent after legal prep costs about $25k. I can think of many ways to reduce the bottleneck: restrict the length of the disclosures and number of drawings, standardize templates and classifications. Make the filing free and get the fee by taxing the user of the patent. This guarantees revenues for all producers,reviewers and users of patents. Why would anyone want a delay in patent granting?
Note to patent examiner : do not read this if you are reviewing my disclosure :-). Too late for that I guess...