I also upgraded last night and went flying this morning, pleased to report no obvious issues although I only got through 2 sets of batteries. Had an issue with my X4S camera yaw, it would not work in flight although it seemed fine on the ground, X7 worked with no issues at all on the same settings. I realised that I had not updated the X4s to the new firmware when I got home so updated it as well and now all is working fine at last.
As far as the actual upgrade went it took me about 4 - 5 attempts to download the software and it crashed the first time I tried to update at around 55%. Rebooted everything and tried again and it all went thtough without any further problems. So far I am a very happy Pro Pilot ;-)
I am following the excellent advice from Ian at MadRC (check out his youtube channel) I have set C1 button on Cendence remote to show batter levels, take off fully charged at around 4.25 volts on every cell or better. Land at 3.70V (as per CAA requirements). I did tests running the batteries down to around 3.6V but was flying at around 2 feet for the last 5 mins or so and pleased to say no issues at all. I would not be doing that at altitude mind you after the recent shenanigans.