I just had my flickering SP4 replaced by Microsoft.
This is the second time it has been replaced. The first time was in Jan 2016, 2-3 months after I purchased it in Nov 2015. The issue at the time was overheating causing the fan to run constantly at full speed.
This replaced SP4 then began flickering in Feb 2018 just outside the 2-year warranty period. I spoke with MS Surface support a number of times during which they tested my Surface and agreed that there was a problem warranting replacement. However, when I followed up with MS they advised that I was not entitled to a replacement. I had to push hard to get them to honour the replacement. It may have helped that I have a business Office365 account (Exchange, SharePoint, etc) plus I was posting the Flickergate URL on every blog and MS advert that I could find.
In the course of my conversations with Surface Support it became clear that they were well aware of the flicker problem since they mentioned that they are receiving reports every day but they are being 'vague' about the cause and solution. My view is that the problem may require replacement of all SPs and that is too big a problem for MS to contend with.
I am not confident that this second replacement will last since I note that the Serial Number is much lower than my previous SP4 so it may still have the flicker problem if it is a refurbished device. I have yet to stress load it. At least if it fails again it will have given me more time to operate until the Lenovo X1 (2G) tablet is released.