Hi, I just took the plunge and upgraded my set of 3 Deco M9+ V2 from firmware 1.2 to 1.4.0 using the Windows 10 upgrade tool, and then upgraded further to firmware 1.4.2 using the Deco App on my Iphone 8. All went well, no problems. Each upgrade took less than the upgrade tools indicated, it was all done in less than 3 minutes for each step. So that seems just fine.
I did the upgrade to get access to the web interface for the Deco M9+ router and that worked, but the functionality in the web GUI seems very limited indeed. I would expect to have all the controls as is currently available in the mobile app, but that does not seem to be the case. So my expectation is that this is improved.
I did find a bug in the Web GUI, it does not show the correct Deco unit names. In the mobile app, the main Deco is "Living Room" and the other two are "Basement" and "Study". But in the web GUI they show up as "living_room_1", "study_2" and "custom_3". See the screenshots.
While this is not critical, it is a bug that shows that the Web GUI is not really well tested. So please update it to be equivalent to the mobile app.