(I'm not sure how this applies to other Apple devices but I had the following experience with an iphone 4S and an IPad. (2010 model))
Don't forget that if you update to iOS8 some of your settings will reset back to the Apple default so if you are anything like me paranoid you might want to go through all your privacy and security settings again.
I was a bit
to see that the update had turned on in app purchases and had changed the time required before having to re enter your Apple password to purchase apps etc from immediately to 15 minutes. You would have thought Apple would have learnt from PREVIOUS EXPERIENCE. Presumably the $32 million fine wasnt enough..
The iOS8 update also reset my privacy settings from the most restrictive settings to the most permissive ones.
I don't want Apple to track my location and send me location based advertising and I certainly don't want search based adverts either (etc, etc) . If this is the type of thing that bothers you then you can use THIS GUIDE to show you how to sort it out.
BTW, I know this won't apply to everyone but I also had to reset my GOOGLE AD PREFERENCES as I don't like receiving search based ads from Google.