I see iOS 11 like Windows Vista / 8 were to Windows 7/10, the unfinished version of the OS. The banana product.. send it green, let it mature in customers hands.
iOS 11.3 seems to give back the speed of my old iPad mini (2nd gen), the keyboard was specially laggy and I presume it was the OS under powering the CPU. Now it is quite more responsive, although I don’t see any option in the battery section (settings) like in the iPhone.
I think I’ll be fine with a two year period between “mayor” os updates if that period brings really finish, polished OS.