I'm on a corporate plan with Telstra for a personal phone - about $3 administrative charge per month, no minimum spend, $0.16 SMS.
When I moved into my new house, before I got the broadband on, I had internet withdrawal and used the browser on my Nokia 7710 over GPRS (ie: non-3G) for a bit. Web pages only, no video or audio. Big mistake. In no time I had an $80 data bill, several times higher than my mobile bill has ever been, almost twice what I pay for my 20GB monthly broadband access. Swore I would never use it again, and I haven't.
Someone is going to have to do a whole lot of convincing to get me to use mobile internet on any phone ever again, particularly given 3G is a more expensive service than even that.
Don't get me wrong - I *want* to use it, and would love to be zooming around with an iPhone, using Safari and Maps and all that other stuff, and even without using those I still do want an iPhone; with 802.1X coming in iPhone OS 2.0 I should be able to happily connect to my company's wireless network. But as far as mobile internet goes, once bitten, twice shy.