Whoever told you (OP) that is severely misinformed.
$29.99/month grants you unlimited 3G data on the device.
This excludes any hotspot services.
That costs an additional $20/month, allowing for 2GB of usage.
Hotspot overage is $20/GB.
Someone mentioned iPad data not being unlimited anymore..
iPad data has never been unlimited.
iPad plans with the Mifi unit are $20/1GB, $35/3GB, $50/5GB, $80/10GB.
Those iPad packages are slated to stay the same for the iPad2 as well.
Data packages will likely change to tiered plans, but there are no plans for that in the near future.
I would estimate them moving to tiered data for all devices near 3Q/4Q of this year.
Cheers.
*edit
I misread the iPad data comment. Instead of removing what I wrote, I just want to correct myself, letting that commenter know I read what they said incorrectly.
[sent from my android]