SIM not replaceable, BT DUN
Take this with a pinch of salt:
The 3G iPhone isn't SIM replaceable.* The SIM card is put in the phone as part of the manufacturing process and is not replaceable by the user.* This will certainly curtail unlocking efforts.* According to our source, you CAN remove the SIM... "with a hammer".* This conflicts with the "sim ejector tool" that Apple has listed in its parts box for the US.* We'll see how this develops.
The 3G iPhone WILL allow Bluetooth Tethering for laptops.* We asked about Wifi tethering and got a blank stare.* We'll take what we can get.* They said that this was 99.9 percent certain and "Apple can always change their minds".* Since O2 controls the network and costs involved the decision would largely be theirs.