Having been part of the original " iOS fucked my phone" angry gang when my 4 was nearly killed by an update ( incredible slow etc, dd kept it for a year after though so it would have been nearly 3) it's alk hapoened again with ios8 and the 4s.
HOWEVER dh who is a late entrant to the smartphone market with a nexus4 . The latest lollipop updates have buggered that too basically ( and it's not just slow, it's not ringing and important things, and the outlook app is buggy etc).
My feeling now is that at 2yrs old the computing power is so outdated we can't expect phones to update any further and handle the software requirements. What do you think?
If so why can't the Giants of technology maintain different levels of iOS for each level of phone eg ios7 for 4s and a bank of iOS compatible apps to keep those phones running . Yes it won't be up to date, but you'll still have a working phone...