I currently use a Droid 1 running Gingerbread. I rarely make phone calls, maybe one or two a day. I predominantly use it for reading email/Gmail, checking bus arrival times, and maybe reading a few news stories. On weekends or evenings I might send 5-10 text messages. I also use it as a music player on the bus a few times a week. It sits idle in my pocket most of the time.
I do NOT run tons of widgets and apps that need data like Facebook, Twitter, YouTube, Gtalk, etc. My apartment and office have good wifi coverage that I try to default to when possible. I live and work in downtown Chicago so coverage is quite good and is definitely LTE.
When looking at my usage on my Droid 1, I typically see this:
26% phone idle
20% cell standby
Does this sort of usage make the Thunderbolt a bad idea? I refuse to buy the extended battery. All I need is for it to last until dinnertime when I get home, frankly. I know the Droid Charge is coming but I prefer the sturdy build quality and glass display of the Thunderbolt, especially after having an all-metal & glass Droid 1 (and iPhone 3G before that).
TL;DR: I am not a heavy data user, I just read email sometimes and make a few phone calls/texts.