I'm on my second white one.
I pre-ordered one and it arrived on launch day. The volume buttons were loose in the housing and rattled when the phone was shaken. Admittedly not a life changing problem, but not something you'd expect on a £529 phone, especially when the iPhone 4S and 4 which I had previously didn't suffer from it throughout their whole lifetime.
Also, the metal band scratches up INCREDIBLY easily. Mine had marks on it straight out of the box. Apple have obviously used the cheapest, weakest anodising they thought they could get away with.
I got in touch with Apple to report these issues and they sent a replacement out straight away, no questions asked. This lead me to believe that mine wasn't an isolated incident, and after Googling it it's apparent that lots of people have had the same thing happen to them.
My second one arrived, marked out of the box and with the exact same problem regarding the rattly volume buttons. I've decided to keep hold of this one as I'm pretty certain that if I got it replaced again, the third one would be exactly the same.
Apart from this, the phone has performed faultlessly and is faster than my 4S. The battery is also better than the 4S, but not as good as the 4. The slightly bigger screen might not sound like a big deal, but it does make quite a difference. The screen also has a different pixel arrangement, so colours are slightly richer than on the 4 and 4S - something which is immediately apparent when the two are held side by side.
So, to sum up:
- The bigger screen DOES make a difference
- It IS faster
- The battery is better than a lot of its competitors (believe me, I've tried them all!), although not as good as the iPhone 4
However:
- The Volume buttons WILL rattle slightly in the metal band.
- The metal band WILL scratch up (much like the metal bezel on the iPhone 3G/3GS did)
If you've got your heart set on getting an iPhone, get the iPhone 5. The issues that I've mentioned above are very very minor and don't detract from the overall feel or performance of the phone at all. I don't notice the volume buttons rattling unless I shake the phone and listen for it.
Android fans need not reply, as the OP has asked specifically about the iPhone.
Hope this helps. If you lived closer I'd have happily let you use mine for a few days to see how you got on with it.