I usually end up using like 2.1GB a month, but that's with me kinda monitoring it and switching to wifi any chance I get. When I first got this phone, I'd go over 3GB regularly. My battery has been complete shit for a while now, so I haven't been streaming or doing much on it at all recently. Just twitter, instagram, and listening to downloaded music.
Main reasons why I haven't already jumped to T-Mobile is because I'm still on a family plan that I'm not paying for, I hear their 4G is slower, and their service still has a bad rep.