Yesterday whilst I was in Asda (UK) I was playing with one of their iPad Mini 2's, and checked what the IOS was, and it was IOS8.1, the same as I downloaded on mine. The iPad Mini 2 in the store was flying, and amazingly quick. I could not check the Safari browser on it, as there was no wifi.
Conclusion: One thing is for absolute certain, the IOS8.1 is definitely not for older devices, and my iPad mini (the original iPad Mini 1) is still so slow after downloading IOS8.1, and comparing it to the Mini 2 in the shop was like night and day - but of course the iPad Mini 2 has the A7 chip, which CAN cope with the latest IOS.
Sadly, it seems that Apple is absolutely, and purposely slowing down older machines with their updated IOS.
That is fine, as technology moves forward, BUT why would Apple destroy people's older devices when they know full well that they will struggle to load the latest IOS, and have performance issues. Not only that, but Apple are rubbing customer's noses in it by refusing those with older models to revert back to a WORKING IOS.
"Now that you have downloaded the latest IOS on your older machine, you can do nothing about it's poor performance.... we know you could go back to a working IOS, and we have it, but we will NOT let you do that....why?.... because we want you to buy a newer model and increase the profits of our company even more.... simple as that....welcome to the Apple prison..... (hehe)..."
It is almost blackmail, and maybe ethical (or is it....I wonder!), but it is certainly not moral.