i usually use about 1.5-2GB every month. Most I've ever had was 3.5GB but I had to try to get that. I don't tether because there is WiFi everywhere I go. So far this month I'm at ~1.4MB that's with an hr of last.fm streaming, occasional YouTube vids, FB browsing, Phandroid app, Twitter, web browsing, etc. Oh and email and such
I'm 1/3 through my billing month and sitting at a svelte .104 gig. I usually average betwen 1/2 and 3/4 gig. My wife will average around 1.5 on her iPhone from watching netflix from time to time. I've only gone over a gig once, the first month I had the phone. I've used wireless tether until the gingerbread update, but only occasionally and for short durations.
I'm a heavy data user and I used about 6 gigs on 4G my first month on my Droid Charge. Didn't really tether except for the two nights that storms knocked out my UVerse for a bit. I usually used 2-4 gigs on my Sprint Pre.
I consider myself an average, medium user. I use Slacker a few hours a week, browse internet, use apps and Google Navigation moderately. I don't download movies or video chat as I'm stock. Never use wifi. I use 6GBs a month.
Somewhere between 1 and 8+ gigs a month. It really depends on the amount of WiFi I use. Even though I have the unlimited plan I am pretty religious about using WiFi unless I am on 4G then it's almost always faster.
My mom was in the Hospital for almost a week and I spent a lot of time there and I used nearly 4 gigs in a few days. They have the crappiest WiFi ever, and least there was a good 3G connection.
If/when Netflix ever happens it will go up a whole lot.
I use at least 30gb. Where I live, there is no high speed internet. I tether and play with alot of different roms (I'm rooted). Hopefully the rumors of being grandfathered in are true. I would literally have to change my life to accommodate a limit on my data usage. Lol, sounds exaggerated, but unfortunately all too true.
I don't stream or tether and I'm on wifi at home at night. During my 8 hours of work during weekdays the only thing that uses much data is doggcatcher occasionally downloading a new audio Podcast episode. I've never used less than 5 gigs a month in the year i've had my DX. Never more than 7 though. Seems like people that use their phones at all are going to be screwed by these new plans. might be fine if you're on wifi all day everyday.