My conclusion from an earlier blog relating to the IOS8 update, is that I can not find any benefits outweighing the main disadvantage.
I have IOS8 updated on my IPhone and my IPad.
Initially, it was possible to backtrack and re-install IOS7 and alas, I did not take advantage immediately of what was a temporary opportunity.
It is now not possible to download or restore IOS7. ( It is in fact possible if you are in the business of tinkering with system backups, have time on your hands and avoid the numerous pitfalls along the way, but otherwise....)
The initial IOS8 release was a bit of a nightmare and so, on the upgrade issued a few days after, I installed it straight away which did eliminate many of the major problems.
For me the drawbacks seem to be more apparent on the IPad.
A few weeks on and the various apps I continue to use as normal (ish), but my big gripe is that the overall system lags and drags.
When logging on to the IPad using the 4 digit passcode, there is a very perceptible delay whilst the system assesses and passes as accurate the code to the extent that you think you have missed a digit or input an incorrect digit, so you repeat the process - ( I was never really even aware of the "delete" option at point of logging on prior to the upgrade; it was that slick.) and end up doing everything twice.
When pasting copy or attempting to highlight specific areas of text to copy or edit, (the latter which has caused me to reach for the desktop on more than one occasion) the delay makes the selection process almost "not fit for purpose"
When closing down a window, I find myself closing it twice, because it does not respond immediately, when in fact it is still thinking about the first closure request.
As a result the window closes, but then as the system follows the commands issued sequentially, the window re-opens and still in the same programme.
I do like the new autospell which seems to be pretty good, very intuitive, but other than that, I would have preferred to stick with IOS7.
So my advice is that if you think that you ought to upgrade, because it is going to be a better experience with some slick whizzy bits, then in the first instance, review the specific areas that apple have highlighted and if you can really identify an area or facility that is going to benefit you and you use it a lot, then go for it.
For me at point of writing this is somewhat reminiscent of a windows system upgrade, rendering your cpu inadequate and the replacement of your RAM a necessity.
No doubt things will fall into place and the overall benefits will become apparent, but for now, my daughters Acer tablet, with a 7 1/2 inch screen using an Android operating system is a lot more lively and responsive than my IPad.
In the meantime, patience, it would appear, is the required attribute.
PS: I've just installed Yosemite - more later!