Thanks a lot so far!

After some investigation and testing with Windows XP I found out that the OBEX channel is blocked if you have the PC Suite installed and running. (it is automatically running at startup by default) - if you quit the PC Suite you're able to use the device driver.

This is suboptimal for a common user. I'm able to imagine myself the questions and help requests at this forum only because the shitty PC Suite is running somewhere in the background.
Hmm... and if I need to change at linux the udev rules... hmm... no. I don't like this requirement. And if I could only use the PC Suite Mode at Linux and not Windows I guess I wouldn't chose this type of connection.

So I guess I will see how Bluetooth works in detail... otherwise transfering data over a socket connection is the probably best solution.