iPhone review part 3: User Interface
Over all, the user interface is good. It's uncluttered, and navigation is easy, but some features are rather poorly implemented.
Managing settings could be better organised. Apple provide a way for applications to drop their own "preference panes" into the global Settings application. Unfortunately, not all apps actually do this - some have it as a seperate screen inside the app - so unless you remember which app works which way, you have to guess which is which. I can see why Apple let apps stuff their preferences into the Settings app, but if that's what they want developers to do then they should enforce it. That sort of quality control is what their acting as gatekeeper to the App Store should be all about. My own preference, however, would be for apps to not do that. Given that third-party apps can't run in the background, then changing settings inside the app is most sensible, as when you realise you need to change a setting, you wouldn't have to quit the app, go elsewhere to fiddle with it, then start the app again.
Those poorly implemented bits of the user interface are many, and I'll just mention a couple of them. Most of them are simply to do with features being entirely undocumented, with no visual cues that they might exist. For example, if you want to type é, it's easy, you just hold your finger down on e on the on-screen keyboard until a little menu pops up, then slide your finger to the right letter. This is so useful, but I only discovered it by accident.
And then there's the terrible implementation of copy and paste. The much-vaunted cut-n-paste that Apple unaccountably left out of earlier versions but now trumpet as being a reason to buy from them (as if no-one else offered it!) relies on you double-tapping the screen very precisely. Given that you have to use the fleshy part of your fingertip and not a stylus, this is almost impossible, and so it's a lottery whether you get the cut/copy/paste popup, or the select all popup, or whether it selects some random blob of text and gives you the cut/copy/paste popup. Madness. What's wrong with having a drop-down menu at the top of the screen and mandating that applications leave that area alone? That area normally contains a clock, battery level indicator, and signal strength indicator, so that's Useful Information that should be left alone anyway.