Some of us prefer non-commercial messengers, so support for XMPP voice and video calls would be great. Now that GTalk voice and video calls are there it might be even quite easy to add.

As it is the XMPP text messages work nicely from N9's default message app (though account activation GUI is disabled, so I've had to help my friends and family to add their accounts via command line).

[edit] XMPP voice and video calls actually do work after installing Gtalk Video Call add-on.

Go to phone application > find an xmpp account from list of contacts and touch it > call screen appears > touch account name below the contact (where the phone number would normally be). During the call you can switch from audio to video call by pressing the video camera icon.

Lots of thanks to people who made this.