Wow, you guys make me feel like some kind of freak.

Here's an outlying data point for you. I have an HTC Incredible and I have used over 2 GB in a month, and almost always use more than 1GB/mo.

I do use Pandora very often, so that's probably a good chunk of my usage, but I think you'll use more than you expect unless you're always around WiFi. There are so many apps available that once you start playing around with it, you may end up using it more than you'd expect.

If you start out with a low usage plan, keep an eye on it closely; it gets expensive if you go over and have to pay per MB!