I have the iPhone as a phone. I make calls with it, keep it in my pocket, and other uses are secondary (albeit common). Insofar as it's uncomfortably small for some uses, that's why an iPad is usually in arm's reach. Sure, 5" is more usable for many applications than 4", but ~10" is much more so. Make the phone more than 4" and I'm apt to just not carry it, as it won't reasonably fit in my pocket and looks/feels like a wall held to my ear.
iPad + iPhone Nano = winning combination. If Apple makes a 6" iPhone, I'd sure hope they at least retain the 4" version, if not shrink & optimize for a much smaller version. I need a phone that excels at being a phone and integrates well into the iOS ecosystem; got my tablet for applications needing a more complex/larger interface.
While there are a lot of people who share your use case, there are probably a lot more people who don't.
Which is why the product diversity on the market right now is good. There's a decent chance that you'll find a phone that will work for your particular use case.
What concerns me (and I'm sure many others who don't like the idea of a larger iPhone) is that the iPhone 5s is currently the only flagship phone under 4.5". Sure, you can get smaller budget smartphones, but if you want a small high-end phone, it's Apple or nothing.
If the rumors are true and Apple decides to make the iPhone 6 4.7" and 5.5", what do I get next time I'm ready for an upgrade? I think it's silly for Apple to leave money on the table by only selling the current form factor when there's obviously a lot of demand for a larger iPhone, but it's equally silly to ignore the market for smaller phones like every other smartphone manufacturer is.
I feel the same way. If I were designing my own iPhone, it'd be as light and thin as the current-gen iPod touch, but with the height (and so screen size) of the iPhone 4 series.
iPad + iPhone Nano = winning combination. If Apple makes a 6" iPhone, I'd sure hope they at least retain the 4" version, if not shrink & optimize for a much smaller version. I need a phone that excels at being a phone and integrates well into the iOS ecosystem; got my tablet for applications needing a more complex/larger interface.