Give us iChat! Complete with threaded text discussions like iChat for the Mac. Make it run in the background so that we can be logged into IM all the time and receive instant messages when our phone is asleep. Give us ringtone and vibration settings to alert us of new IMs. Make it work with the Jabber, AIM accounts that we use with iChat on the Mac. For bonus points add support for MSN and Yahoo.
When working with multiple pages in Safari on iPhone, previously loaded pages are sometimes reloaded when you navigate back to them. A setting to increase Safari's cache limits would be useful especially for ajax web apps, like google reader, that force you to start from the beginning when they are reloaded.
Make the entire screen clickable when I take a picture. Not just the tiny button that is impossible to locate when you try to take a picture of you and your friends. Or maybe make the volume button the shutter button?