I bought an iPhone a month ago and I love it. Let's start with that. But don't anyone think for a moment that I'm not keeping tabs on the pluses and minuses.
The first big, big minus I have to share is the fact that there's no interface on my computer to use the phone while it's plugged in.
The real inconvenience here is that I only have two ears and hate switching headphones between my phone and my computer. I get a call, I plug into my iPhone. I listen to a podcast, watch a video or listen to music, I plug into my Mac.
I have an iPhone -- I want a MacPhone too!
The solution is to either bring the phone functionality to the Mac (in an interface much like Skype's) or to be able to pass computer sounds and mic-in through the iPhone while it's plugged in.
The photo below shows how a feel about this :-)