Julien,

All my Apps seem to work fine. I've got a 32gb iPad and is almost depleted of space as well. I like to do scratch takes of my song writes on it and that burns up storage fast. Most of what's on my iPhone is music and photos. I back up photos to the computer and rotate music on iTunes by checking or u checking the sync boxes. It's also good to connect to iTunes every so often to do a complete back up of the phone.

I've read a couple of articles which advise against updating to iOS 8 if you have a 4S or earlier model. It requires processing power that the 4S just doesn't have, uses more memory and its UI has been designed for larger screen sizes. My girlfriend updated (even though she's just about to get a new phone) and regretted it - apparently her battery life is now terrible and apps are very slow to open. Having said that, I've read comments under these articles from people who say they updated their 4S's and are having zero problems. It seems these OS updates affect different users in different ways. 
 
I'm holding out for the 6 Plus, but as is typical with AT&T, their trade-in deal makes no sense. They are touting $200 credit if you bring in your old phone in good condition (which mine is). However, you have to bring your phone in by Sept 30th according to the woman I spoke to...but the 6 Plus is not shipping until November. Which means that if I want to take advantage of this deal, I'd be without a phone for over a month. Obviously, nobody is going to go with that "deal." It's ill thought out, ridiculous and a kick in the face to people like me who have been loyal to them for over a decade. The girlfriend also had a similar deal with Verizon, but they capitulated and extended the deadline to return phones for trade ins so that 6 Plus customers could take advantage. I don't see any signs of AT&T doing that yet. 
 
They do have some kind of frequent upgrade plan now called AT&T Plus or something, in which you pay an extra monthly fee ($40 I think) and get a phone upgrade every year. I can't work out if it's worth it or not. Probably not. 

Some things don't work with ios 8. IK APPs do not seem to be updated to work with 8 but they do work, they wont work with Audiobus. I have another APP Guitar Tone from Sonoma Wireworks. It just automatically closes after a quick message about not connecting with Audiobus. I deleted Audiobus but all my APPs still give me a message about not connection with Audiobus, except GarageBand, it works with Audiobus. I thought that deleting Audiobus would resolve things until IK gets around to updating but it is as if it is still there. Most APPs just disable Audiobus but Guitar Tone just closes. It is actually still open but minimized, in other words, if I press the front button twice, the app is still running, if I open it, it crashes again. I restarted but it as if Audiobus is still there. I guess I will get Audiobus back from the cloud and just not use Amplitude with it until they update. I'll try to contact Sonoma to see what is up with their APP.
IOS 8 enables every APPs notifications, you need to go in and manually disable them again. I'm not sure about the Cloud Drive if you use a Mac. It seems to work with the Cloud Drive for windows but I don't think it will work with a Mac until the release of their new Mac OS.
 
Oh well, maybe I should have waited but I didn't. My phone is a 5 so maybe everything will be OK.
 
Thanks,
Julien