I just got an iphone 4 and, being a bit of a luddite, I'm absolutely delighted with it mainly because I don't have to umderstand everything in IO540's post to use it. So far I've only downloaded a couple of apps, orbifly, pilotwiz and NOTAMS.
Actually, as I write I find I'm making a fool of myself because I haven't worked out how to get the NOTAMS function to work......
Still, I'm very pleased with it and if someone wants to show me how to get the best out of it I think I'd like it even more.
A year or so ago I tried a Blackberry but sent it back after four days because I couldn't work out how to use it.