Tethering over Bluetooth is slower but being wireless is a great advantage over USB.
Another simple setup:
1. Install Dial-Up Networking (bluetooth-dun) from Extras on the N900.
2. Install blueman Bluetooth-Manager on Ubuntu. This is not required but a good gui doesn’t hurt.
sudo apt-get install blueman
3. Open blueman from the status bar and pair the N900.
4. Right-click the connection and select Dial-up Connection.
5. Select the T-Mobile connection. If you haven’t yet created a Connection, see my previous post.
Ovi-Suite is a good tool here.
1. Install Dial-Up Networking (bluetooth-dun) on the N900
2. Open Ovi-Suite.
2. Connect the N900 via bluetooth (Tools -> Add New Device).
3. Select Tools -> Connect to Internet