So after a 2 days on the stock Thunderbolt battery I'm thinking the battery life is pretty much like the Incredible.
My setup:
I have the stock battery
I don't use the Sense widgets, I found on the Incredible they use a lot of battery.
I use Beautiful Widgets for weather, clock
I use LauncherPro instead of Sense too.
I have my screen at about 25% brightness, still easy to see
Run on wi-fi at home
I live in a 3G area, work in a 4G area. Yesterday I was at home all day and I had 3G, 2 bars most of the time.
With that said, day 1 my battery was awful. I let it charge all the way but I got about 6-7 hours out of it before it was pretty low. I didn't check the percent, but it was low enough to turn the battery indicator orange. I think the first day will be bad be cause 1) We're all gonna play with this thing, and 2) It will automatically download all your apps from the Market that you had on your old phone if you came from Android. At least it did for me. Who knows how much other data is being sync'd when you first set it up. Also, I transferred over 16GB of music to the phone and was using iSyncr wifi-sync. I'm sure that will kill the battery.
Side note, anytime I flashed a new ROM on my Incredible, battery life always seemed a crap shoot in the first 24-48 hours. After that though, things always got better. Could be the same on first time use of any phone like the Thunderbolt?
Day 2, I went over 15 hours and I was at 41% battery. I have a separate cell phone for work, so my personal phone is purely for personal use. This means I am on the phone about 5 times a day, not often, for about 20 minutes on average. I send/receive somewhere around 50 txt's a day. I check/send about 15 e-mails a day. I do spend a lot of time on Google Reader. Every couple hours I end up with about 200 new things to read. I surf the web on it a good amount too, watch Youtube videos, etc.
So, I gotta admit, after the Incredible, the Thunderbolt does not seem any worse and may be better. In fact, 41% after 15 hours would have been real tough on my Incredible until I flashed ROM's on it like CM7.
So 2 days later I want to follow up on what I posted previously. Yesterday I had decent battery life again. After being on the stock battery for 12+ hours (just over 12) I had 39% battery remaining.
During the day I did some more wi-fi syncing of music, and then my usual surfing the web, watching YouTube, sending texts, reading/sending e-mails. I also run Trillian all day for AIM, Yahoo, GTalk, and Facebook chat.
Today I switched it up. When I ordered the Thunderbolt, I assumed I would need the bigger battery so I got it, but I didn't crack it open until after a few days with the stock battery. The extended battery is a beast! You can definitely feel a little extra weight.
On the other hand, I never imagined it, but the position of the hump of the battery makes the phone pretty comfortable to hold. I mean both to your ear and when you hold it in your palm, looking at the screen.
Coming from the Incredible, this phone is a bit bigger anyways, but I am finding that I need to get used to the Thunderbolt in my pocket with the extended battery in place.
More importantly, the extended battery lasts waaaaaaay longer. I've been off the charger now for 11.5 hours and I am at 70% battery. I did turn off my wi-fi during the day while I wasn't home, so it was purely running of the mobile network all day while I was at work, 4 bars of signal.
A few other notes about how often I have things syncing: The only accounts I have active in my accounts setup are Facebook (from the Market, not for Sense), Google, and Twitter (again form Market, not for Sense). I have them setup only to update once/hour. For Google I am syncing Reader, Contacts, Gmail, and Calendar. I had Trillian running all day here too.
Display 63%
Cell Standby 9%
Phone Idle 8%
Android System 4%
Internet 3%
Voice calls 3%
Android OS 2%
GMail 2%
Google Reader 2%
Wi-Fi 2%
Beautiful Widgets 2%