Well I've had my 5 since release date. I love all my apple products and could never convert. But here are my issues in no particular order...
Would've liked a bit more wider on the screen.
Battery life isn't as good as the 4s which is a bit of a pain.
Maps is crap and we all know it so that's all I'll say.
No YouTube app. And I hate the App Store version.
I'm still trying to get used to reaching to the top left to go back, especially in messages.
Bluetooth interference is a bit more sensitive.
Because I work with my hands I like to use an otter box case which is great. So device thickness is no issue for me. But what really gets my goat is that we keep getting thinner and thinner in device thickness, that we aren't moving forward in adding new features. I would've loved to see an NFC chip in the arsenal because I hate carrying a wallet. Yes it's noticeably faster! And I love it! But I was expecting a lot more.
Oh, and its taking to long for app developers to optimize their apps for the bigger screen.
Apart from that its great and I love the new design.