Mobile Broadband is now tiered, but access for your smartphone is $20 for 2GB/month with $20/GB overage. I consider 2GB on a smartphone to still be "unlimited". Maybe others don't.
I would agree, I have a friend who has a Droid2 and he basically did everything he would normally do to see how much he used. He listened to pandora all the time, surfed the web on his phone and check fb, twitter, and e-mail a lot. Never went over 1gb