Good morning everyone, thought I would add some detail here as I had Zen G.Fast installed last week.
I was Zen's first g.fast customer and the regrade got really messed up and took a few days to sort out and become active which resulted in me losing service. However, Zen's customer support was amazing and they provided me with a LTE hotspot and all sorts as they acknowledged that this was all new to them and needed some figuring out.
Anyway, at install the Openreach engineer measured my line length at 340m from the cabinet (I reckon the straight line distance is about 250) and I am seeing speed tests of 200 down and 27 up (as opposed to my old 80/20 on FTTC). Again, when the Openreach engineer ran his sync test at install he was getting 240 down on a 3db snr profile - so I'm guessing that I am currently on a 6db one and I may get a little more at some point (sorry, I forgot to ask about upstream).
Sadly, with a MT992 + Asus AC68U I have no access to stats and the Zen customer portal hasn't been updated yet so that it can show g.fast stats, so I have no way of knowing for sure and I wonder if the Asus DSL-AC88U has sync rates, snr information etc. that is available from the GUI you can get to by logging in to the router?
Interestingly, pings to bbc.co.uk are now 13ms rather than the 8-9 that they were before, but I am now routed differently from the exchange on g.fast (which was one of the major problems with my install).
Please ask if you have any questions as I will be happy to share more detail of my experiences.