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Personally I miss:

BiteSMS - yes Apple has come a long way, but they still have quite a long road in front of them before I would recommend the native app over Bite.

Flux - since I check my phone several times during the night, this is really a must have tweak. And Apple could have easily included it in iOS 8

Bytafont 2 - this is more a wish than an actual need, I just love the ability to change the font.
 
like most others i miss f.lux, surprised apple haven't brought them out and included it in ios8!

I really miss activator the most, while the 6 sleep button being on the side makes complete sense it makes it that little bit more annoying to lock quickly when on my work desk, simple swipes to lock screen was ideal for me!

also right up there is the tweak that allows you to swipe left and right on the keyboard to move the curser through text fields, can't remember what it was called now though!

I have had some positives to not being jailbroken though, the sky go app working properly is nice, along with a couple of other apps like e-banking.
 
Still waiting on my 6 to get here but I can tell you w/out a doubt the things I will miss

3GUnrestrictor
MyWi (I'm on VZW Unlimited)
Springtomize or at least something that lets you get all the icons off the homepage
iFile


Possibly miss Terminal also, but I don't use that much.
 
I moved to Android *sigh*
I miss the proper movie box app (the ui is really bad on android)
And speed optimisation (not going to root my phone)
 
My i6 was turned on today, and sim from 5s put in there. :( I already miss the customizations available with the j/b.
 
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