I've had a bit more of a play with the device and as a previous Blackstone owner (Touch HD), there are some pretty noticeable differences in the UI which I'd thought I'd share for those who are interested and havn't yet got their own to play with.
Firstly, the start menu has now been totally replaced with a HTC version, which can be disabled it seems by browsing this forum, but TF3D offers no in-built method to disable it which is kind of annoying (see attached image).
Secondly, the TF3D menu style is extended into almost all programs. For example even in file explorer, opening the standard menu from the soft key shows a 'finger friendly enlarged menu' (see attached image).
Also the Bluetooth UI is completely different (see attached image).
Also a welcome change from the Blackstone is vibration feedback when using the on screen keyboard, and it also shows a button preview above the buttons when pressed (similar to the iPhone). Although this will be less useful since the device has a full QWERTY keyboard, but I'm assuming the Topaz (Diamond 2) has the same feature improvements, so it will be a welcome change for users of that device.