I've had my Optimus V since the end of March, I downloaded Droid Stats sometime after that, a week at most later. I have used 481mb total since say the first week of April.
My month is up on the 23rd and I have used 141mb this month.
Now, I do have a stand alone GPS unit, so I don't use my phone for that. I have a stand alone MP3 player, so I don't stream audio much. My kids do sometimes use my phone to stream Netflix while we're out of the house.
I mainly use my Optimus V on 3g for email, net browsing and uploading images to Google+. YMMV