After my summer vacation, I finally did the official update on my defy, which brought the thing to Android 2.2.2.
Since Motorola had obviously done quite some customizing to the original 2.1, not too many obvious differences were there: "Mobile Hotspot" was present before. The design theme (which is something I could not care less about...) was already like 2.2 before and the horrible "MotoBlur" interface is still there, so I thougt "well, it's mostly some bugfixing under the hood".
Today, I wanted to finally look into the bluetooth dialup problems I had with the device: NetworkManager was somehow not happy with the responses to some AT commands it got before, resulting in non-working Bluetooth "tethering". Back then, I did not care too much and chose to just use WiFi instead, but today I decided to look into it.
What can I say? The software update upgraded the Bluetooth tethering from dialup (rfcomm/serial/ppp) to PAN/NAP. Which I like much better as it is more "natural" anyway.
Yet another bug I don't need to tackle anymore :-)
Update: The same is possible using the "Wireless Tether for Root Users" app from the android market. Just make sure that you start tethering before pairing the device using bluetooth applet, I'm not sure if there is a way to add the PAN interface to an aready paired device, at least I did not find one, so just checking the "Do you want to use the device for internet access" box during pairing is easiest.
Of course I don't expect this to work with KDE, but it works very well with nm-applet and bluetooth-applet from GNOME.