I'm focused on iPhone 4 and 5 currently and I use a 640 x 960pt. format. Keep on mind that we have to deal with retina displays though resolution for icons and graphics is very important.
Tests with iPhone 6 AND iPhone 6 plus will take place in a week and I'm expecting some unpleasant surprises.
I spent special attention on the anchors of the objects.
I have objects and elements in the footer area which are anchored to bottom, some horizontal Elements are anchored left AND right. This is aimed to serve different display resolutions. At least I can use same GUI for iPhone 4, 5 AND iPad.
There's still a lot of experience to gain on how to use anchors to get kind of dynamic layouts for same layouts for different devices.
Thanks. That is all good information. However, what I'm after is the font size and field size for iPhone 6. In the Enlighten Touch theme the font size is 16 pt and the field height is 44 pt. I think this works fine for the iPad but it takes up a lot of space on the iPhone. I'd like to make the field size smaller in order to optimize screen real estate, but I don't have an iPhone 6 for testing.
When in doubt (which I am) I'll just leave it as is, though I am curious what other developers have done for field height and font size for iPhone 6.