i have been using high sierra since the GM. I did a clean install on the GM and on the final today, but the read performance on my macbook 12 inch 2015 is still low. 400MB/s compared to 800 on sierra with hfs. I tested it with the GM after a couple of days to be sure that is was not indexing stuff in the background. The write speeds are the same roughly 450MB/s. Can someone confirm this with the macbook 12" 2015 base model?