nitrotech: The 9100T is still quad band UTMS - this is confirmed with mine running on vodafone and showing connected to a WCDMA900mhz site.

You need to keep the same modem version number as lots of people have reported that the T doesn't like the same modem as the international versions and results in poor 3G performance.

I'm keen to understand why is there even a T version when the phone is Quad Band WCDMA??

Most likely because it's been customized with Telecom bit's like the splash screen and 'Your Telecom" icons etc..

I was thinking more of the hardware.. all the 850 3G networks worldwide appear to be named 9100T. Wondering if indeed there is some slight hardware changes in these particular S2 models for the 850 3G networks.. Unlikely but possible.