Since my last blogpost, about installing the Option 505 3G modem from telia on Ubuntu Jaunty (9.04), I have not got it working on Karmic (9.10).
(which is good since I have serious problems with my computer freezing, when connected to some wireless networks - should be a problem with the gnome networkmanager, according to some forums).
I didn't have to compile anything, but only used the .deb packages. So the only thing that required carefulness was editing the rules file, but the instructions are very adequate.
The swedish blogpost pointed out that you might need to install some packages before following the above thread:
sudo apt-get install libusb-dev sudo apt-get install python-all