The current feature set suits me fine, but there are two things that seem to have gotten lost in the technology race...
Battery life.
Screen resolution.
The latter is catching up, with the likes of the iPhone, SE X1, HTC Touch HD etc giving reasonable resolutions. But compared to the rest of the tech' in phones, it's a long way behind.
Resolution is everything when it comes to making the most of the capabilities of a phone. The more you can fit on a page natively, the less fancy trickery you have to do to get a normal webpage (designed for 1024x768+) to fit on your small screen, or the more navigation detail you can use, just to mention two examples.
And battery life.... what a mess we're in. What's the point in having every feature under the sun, if you can't even go away for a long weekend without taking a mains charger with you?
The day I can go away for more than a couple of days but still browse the web, use navigation, listen to music and make a decent amount of calls without having to charge the phone again, will be a happy day