I agree with Jibi. Telstra is also nice for giving direct hotkey access to applications in the Applications subfolders (Vodafone, Cingular, Orange). You can run the Today themes which are still quite buggy but kind of neat. Zen however has been seriously
compromised.
Personally I'm back to Bharti (actually Rogers .284 - same difference) for now but with the Tesltra Vodafone theme replacing the OS .284 Vodafone theme (I just replaced it in the Java folder before loading). When they add some customisation to the Today themes and debug them, I'll go back up. And if they return Zen to its former glory it will be no-brainer.
I did find the Tesltra ringtones to be louder and otherwise, unlike some people, had no obvious problems with it.