Okay, so I've taken my TB to a few places and I must say I'm not liking what I see in terms of reception indoors.
1) In my house, upstairs, 6 ft from window - reception was OK, but I'm in a 4G area and it kept switching from 4G to 3G without even moving the phone. Unplugged it was killing the battery.
2) Took it to a friend's house and in the basement I could not get a signal at all. I switched to his wi-fi and that worked well (battery drain stopped falling off a cliff at that point)
3) Took it to an 'Expo' (large warehouse type building) for a show. NO SIGNAL!! My wife had her Verizon Blackberry with her so I looked at it...STRONG SIGNAL!!
I thought it must be a setting or something, but everything was turned on. I then tried a reboot and for some reason I then got 2 bars...very strange.
I'd like to hear from other Thunderbolt users on your experience with 3G/4G reception so far.