How Much Data is Used Streaming Pandora?

If you are like me and like to use your Android or iPhone to stream Pandora in the car.  How much data are you using and should you worry about going over your data allotment.  It would take an average user 4.5 hours of streaming Pandora on a slow AT&T 3G connection (578 kbps) to max out the entire 200MB monthly data plan limit.  Be careful if you are using the AT&T $15 per Month 200MB data plan on might recommend with the 2GB per month plan.  The 2GB per month plan is just $10 more for the $25 per month on the AT&T DataPro plan?  The 2GB data plan prof will get you 45 hours of Pandora music instead of 4.5.  However, I always recommend using free Wi-Fi when streaming Pandora possible.  T-Mobile HSPA+ has works pretty well around the LA area for streaming and would appreciate any feedback from others on their experiences streaming Pandora on Verizon, Sprint and AT&T in other parts of the U.S.

Related Stories:
Why Pandora Could Be The Next Google
AT&T Wireless Data Plan "Bytes"
Why DataCaps Are Killing iPhone App Market