This is a great thing for the web. Like it or not react seems like it is here to stay as the primary web framework for the foreseeable future. There are so many react websites out there that are not well optimized, this is basically like a magic wand that will speed up a huge amount of existing websites/apps without major code changes.
The ROI of this compiler when you consider applying it to the whole ecosystem is mind blowing. Great job react team.