I have a 3G AT&T Tilt. I'm on the 450 minutes (WITH ROLLOVER

), unlimited texts and the Media.NET Unlimited plan. I get a 24% discount thru my company and I usually pay around $55 a month for it.
450 minutes = $39.99
Unlimited Media.Net = $19.99
Unlimited Texts = $9.99
Total: $69.97 + taxes.
I used to use the same plan for my iPhone until I sold it. I have no plans on moving to any other plan when the 3G phone comes out. I will just unlock it and continue as I did before.
I Sling a lot and tether to my laptop, and use about 2->3 gigs a month.
I can see AT&T charging people for the PDA plan ($39.99) for the 3G iPhone.