A downgrade it's a step back, and for all users. If apple has to put so much efforts in supporting an older SO, they wouldn't put the same effort on the newest OS, services, etc.
I think that the update system it's remarkable. I remember my first iPod touch, one day I updated it and voila, now I have apps. (yes, i had to pay but for a few euros i had a totally new device). My 1st generation iPad mini runs iOS 8 in a acceptable way and it's a device with more than 2 years old.
I'm talking based on my experience and i'm not the kind of people that buy a new device every year:
iPod touch 1G - bought in 2007, sold in 2010
iPod touch 4G - bought in 2010, sold in 2014
I'm happy with all the support and updates received and i've enjoyed the devices from day 1 to the last.
If someone downgrades to the pevious version that worked well for then, what effect does it have on other users? Why does it matter to anyone even? It works better for them then how could it be a step back for those people who would get exactly what they want if that's what they want?