The T68i is now accepting data over BtOBEX. It does some things differently in the RFCOMM connection establishment, mostly regarding compatibility between the 1.0b and 1.1 versions of the Bluetooth spec and the use of the Poll/Final bit. Also, there was a small bug in Blunt. I'll have to test my changes with some other devices and also GPRS, but the T68i looks promising at the moment.
... are currently an older BT2000E Bluetooth card and a SonyEricsson T68i. Thanks go to Ronnie and Marty for the loaners! A quick examination showed that the BT2000E is probably a tough case (the serial chip is using some unknown parameters), but the T68i looks better (it has some problems on the highest RFCOMM layer). More soon.