Hi Dan,
Honestly NO!!!...
Really the iphone is very, very underpowered compared to even a basic computer and in addition has java / browser disabilities!
A couple of years ago I retired my HTC pda, which really was more powerful than the iphone is even now.
Basically the screen size, hassle of typing and lack of computing power makes these items pretty useless as a real tool (and as I say, the iphone is even worse!).
Finally I got past the BUZZ that my pda could do everything and that it was cool - and moved on... I was a big fan by the way

lol
What I decided to do instead was use my phone, as a phone / music device and upgrade to a small notebook (e.g. macbook or 10" to 12" notebook) - which has worked great, as it is easy to carry around in a small bag or side pouch and these days these items have computing power past what is needed to run even link-assistant tools on the run (assuming you can get a cheap unlimited 3G data plan).
I hope comments help - cheers, Asiaplay