Stephen,
There has to be an explanation for why some people have found solutions yet those don't work for everyone. No one's situation is identical. We are all using different model iPads, upgrading from different iOS versions using wireless or hard connections, have tried different tweaks or patches, are using different apps, etc ... having spent 12 years in I/T, I know that each of these scenarios can influence the results people get when they try a suggested 'fix'.
What I meant by "I'm thinking there's no one guaranteed solution for everyone as it depends on what went wrong on each individual iPad during the iOS 8 upgrade" was that I think the reason why some people (like me and Jeff12, for instance) were able to get resolution with a simple clearing of the cache is because what the upgrade broke or damaged in their particular case may not be the same as what the upgrade broke or damaged on someone else's. They may have started out on the same road (upgrade) but took different shortcuts (impact) yet still arrived at the same destination (problem). Hence different solutions for different people.
Regarding your comment, "the fact is, IOS8.1+ on anything older than the latest A7 chips will run mind-numbingly slow." ... the fact is, since clearing the cache, my old iPad is running iOS8.1.2 perfectly fine.
Finally, I'm not sure why you used such a condescending tone in your response to me. First off, I was responding directly to Jeff12, not you, and never suggested that his 'fix' would work for everyone. I was simply saying it worked for ME and was thanking him for his contribution ... so I'm not sure why you took anything I said personally.
That said, I had almost given up hope of ever being able to use my iPad for anything worthwhile, so I hope that Apple steps up soon so that you and everyone else can have your problems resolved. It's ridiculous that this is even an issue.