OK so rather than a single issue moan, or a single positive.. here's my findings so far:
Positives:
So far, I've genuinely only seen one, and that's not being a facetious.
Battery usage on apps, that's a great feature.
So, the negatives:
1) As a very frequent landscape typer (especially for longer emails/forum posts), I'm disappointed that even with a larger screen, the new keyboard is the same size as it was on the five. I don't know what's happened to the five, has they keyboard got even smaller to accommodate for the side buttons that have been put into place?
2) Photos, the loss of camera roll is (IMO) unacceptable, browsing back through photos is now at utter ball ache. This is something I really hope they bring back. Also, having the delete photo's twice? Just why?
3) Safari, since getting the 6, it seems poor as f**k. It freezes a lot, i.e make a landscape post to cs, and it freezes until I turn it back to portrait. Then I can begin using it again. I've also noticed that the "back" button now sneakily involves reloading the page. Which it never did before. To notice this, on iOS7 if you read a thread, then went back, it was still unread until you refreshed the page. Now, you read something, go back, it jumps back, then a second later it quickly refreshes and the thread shows as read. Just slowing things down really.
4) Light double tape whilst in safari, whilst browsing safari if you double tap the home button (not pressing the button, just tapping) the screen splits, leaving a weird blank at the top. I've no idea as to the purpose as it's totally blank.
I'll add others as I go. But overall, it's not a great update. Feels rushed.