Yup, you do need some data plan. The $25/mo unlimited plan is cheaper than my old blackberry enterprise plan, so I'm actually saving money. hah!

Apparently there's a bit of a hack on tmobile where you can sign up for "T-Zones" at $5.99/mo and run some proxy on your phone where you get full internet at only a slightly slower speed than a full data plan. If you want a smart phone on the cheap, it's probably the best (only?) way to go.