General Sympathy and a Word of Unneeded Advice
Have just finished reading this thread and I have immense amounts of sympathy for the phenomenon described - upgrading to a new IOS and then discovering either that a) it doesn't work like it should, or b) it slows your formerly zippy device down to a tortoise-like crawl.
The sad truth is that this phenomenon is not limited to new IOS's for iPhones and iPads - but it's been going on for a long long lonnnnngggg time. And as someone, I think John Flores, pointed out in an earlier post, it's often smarter to avoid doing updates unless a) you have a strong reason to, and b) you're absolutely certain that it will improve and not degrade the performance/attributes/qualities of your device. Of course, determining that isn't easy - it's more and more complicated lately, especially with the evolution of new and newer (like Dumb and Dumber) IOS's which continually pester the user telling us that it's time for an Upgrade and it's soooo easy and we should just click on that little Upgrade button -
Software/system upgrades are potentially irritating and sometimes dangerous. In fact, there's an entire website devoted to users, fans and devotees of older Mac computers and devices who want to continue using their otherwise excellent but seemingly 'outdated' older Macs and devices - and have discovered, among other things, that software/system upgrades are often 'degrades' and/or sometimes the kiss of metaphoric death. The website, for those interested - is
www.lowendmac.com - for Mac users only, alas.
Among other irritations which generations of serious Mac computer users have complained and griped about is the recent dumbing-down of all the Apple/Mac IOS's to resemble brightly-colored and simplistic iPhones. The newer Mac OS upgrades - Mavericks and now Yosemite - have incorporated many of the supposedly simple/cool/advanced features of touchscreen smartphones from the iPhone - but the sad truth is that they mess up the otherwise wonderful/elegant/functional older Apple competer OS's. Not to mention that the phenomenon described at the beginning of this thread - an upgrade which slows down or degrades your device - is equally true for laptops and computers. Apple's Mavericks' OS is an improvement in some ways over previous OS's - but unless you have newer hardware, it slows older machines down to a crawl, as many users (myself included) discover. But I was obliged to upgrade my OS for my desktop and laptop for software compatibility reasons (I needed to get new upgrades) and so I found myself in the same boat.
With regards to IOS 8, it seems to work wonderfully on any of the newer Gen Apple iDevices - iPhone 5 and newer - but, yeah, it would have been nice if Apple had warned everyone about that before trumpeting the virtues of the new system. But it's part of 'progress'. With regards to iDevices, I have an ancient iPad 2 which I'm running iOS 6 on - I NEVER upgraded to iOS 7 let alone iOS 8 - for the simple reason that iOS 6 is way more modifiable or 'hackable' - and can be used with not only cool external keyboards (a must for serious writing on iPads) but also can be 'hacked' to use a WiFi mouse! Try doing that on newer iOS's (7 or 8) - it's impossible - but the older IOS is infinitely more customizable.
The Moral of the story is: DON'T EVER upgrade unless a) you have a good reason to - and b) you're certain that it will work decently on whatever device you're upgrading to. The other classic problem, which I think Christie mentioned, has to do with not having enough built-in memory - aka 'RAM' - in your device. Upgrading an older device to the newer System can cause crippling slowdowns if the device doesn't have enough built-in operating memory or RAM. Unfortunately, with smartphones & tablets, the amount of RAM your device/phone/tablet has can't be modified. With most laptops, desktops, MacBooks or whatever, if you experience a slowdown for whatever reason (and,yes, people, this happens with non-Mac and non-Apple devices as well! it's not just Apple's short sightedness but rather an industry-wide phenomenon that's existed for a lonnnnggg time), you can often cure the problem by adding more RAM. It's a relatively cheap (and often easy-to-do) upgrade that can speed your ancient device up again in a flash.
My sympathies again to everyone who's gnashing their teeth over an upgrade-caused slowdown. But, from my own perspective, I can't really blame Apple for it - it's part of how the entire industry works - and those of us who don't want to replace our perfectly good hardware every 2 or 3 years with something supposedly newer and better, have to deal with the consequences. Incidentally, I'm in the same boat as many of you: I had to upgrade my desktop computer (an older and quite cute Mac Mini) to a newer OS a year ago or so, for what were good, real, and compelling reasons - and have experienced massive slowdowns since. My alternatives have now boiled down to either an expensive (in my case) RAM upgrade - or (more likely) replacing my ancient desktop with a slightly newer, faster (and more RAM-equipped) one. But damn it can be irritating when something that used to take seconds....now seems to take hours.
Miguel