I updated 3 S9's--a B2, B5 and B9.  They are now (after 48 hrs) showing .0039%, .0006%, and .009%.  Comparing number of HW errors is pretty meaningless because it depends on how long the miner has been hashing--to say nothing about how the number of errors in a given time depends on the hash rate--so comparison of number of errors between an S9 and an S4 ought to be adjusted to reflect the different hash rates, even when run for equal times.  The error percentages I am seeing are quite good I think and comparable to those I got with S3's, S5's, S7's and SP20's.  There was a slight improvement with the upgrade to v2.0 but what I notice most is less fan speed hunting, more consistent chip temps (around 90 degrees F) which are well within spec for the chips.  Yes, these miners will get failed boards--one of my S9 B2 boards was just sent for repair (the failure occurred before the upgrade).  That said,  I really like my A721's as well.  

JFB