Just checked this morning and 10 days in I've used 139mb. I picked up the 3gb plan because I figured with LTE I'd be using far more than the old 250mb plan I had in the past.
I have wifi at home, but not at work, so the majority of my bandwidth is just for small things - Evernote, Dropbox, emails, etc. I'll probably keep the 3gb plan though because I'll go over the 250mb plan with LTE, I'm sure. When I had 3G, I was bumping the 250mb limit every month.
Been using it sparingly the past ten days just to see what my "normal usage" numbers would be with LTE. Now that I've got gb's to burn, I may kick it up a notch, do more OTA updates, Pandora, etc. 🙂