I just returned from a trip with the 7100t. I took along a 7230 and a Verizon phone LG4500. Trip was from LA area to DC and down to Quantico Virginia area. I stayed in Crystal city area. Here is what I found:
1. 7100t shows the greates variance in signal strength with units side by side. Anything below 3 bars is very unstable with signal strength varying and as soon as you try and actually use a data connection it is likely to go to no signal. With voice, it will have erratic connection and drop the call. If you can get above 3 bars, the voice is clear and great and the data connection works well for a 40kb system. I used it as a modem and when the signal was good it worked very well.
2. The 7230 usually showed a 1 bar better signal with less variance in signal strength. No modem capability so I couldn't really test data in the same way. I have never been impressed with the browser function on the 7230 even after the mod.
3. Verizon phone always showed a good strong signal (3 plus bars) but lately their service has gotten flakey and even with a strong signal there is a lag between the connection and the other party being able to hear you. Voice quality is not as clear and much to my surprise it drops calls even with a strong signal.
I also tried with the ATT voice only SIM and got a consistently stronger signal, even on the 7230 that only has 900 (not 850) band. This is a major switch for ATT as in the past their signal was always crap.
Finally, I had a major problem with the 7100 where it didn't want to boot up. I am not sure if it was caused by my adding the two new themes posted on this board or the games I added. It took me an hour of playing and finally wiping the unit clean and reinstalling the OS before I could get it to boot up. Maybe it was just an anomally, I don't know. Just a word of warning to make sure you have a backup to restore to.
One other observation to share. Syncing with Outlook has resulted in various strange deletions and changes to my outlook data with users being deleted from my address book and appointments removed. It especially likes to remove appoinments after they have passed, even though I like to keep them to refer back to them. I don't know how to change this behavior.
do I understand you correctly? you have inserted the AT&T SIM card into your 7100t model? I am in a similar boat, but I cannot get the brower working at all with the AT&T Sim card? Any chance you may know?
My phone is unlocked and I am adding BB service to my ATT sim. Once I have it enabled I will let you know. I'm not sure if you need to go to ATT's BWC site and send service books and give it the new PIN and IMEI numbers. Did you check on those?
Unless you are using corporate BES (Blackberry Enterprise Server) for your email, you use the carrier's Blackberry Web Client (BWC). The service books are required on the handheld to control the types of service you are running. The carrier (Such as on T-Mobile) will push the service books to your phone if you go to the site and select having the service book sent. On the BWC site you can register your phones IMEI number and PIN number. This is how it identifies your phone. I have not tried using the Blackberry data service on AT&T yet but hope to in the next few days. Does your phone go to GPRS (all caps) when you have the AT&T SIM installed. If not you cannot get messaging and you do not have BB data service.