Canonical the makers of Ubuntu about to introduce a new desktop notification system proposal. New changes should improve the usability of the Linux desktop including desktop notification system for both GNOME and KDE. From the Mark Shuttleworth blog:
The key proposals we are making are that:
* There should be no actions on notifications.
* Notifications should not be displayed synchronously, but may be queued. Our implementation of the notification display daemon will display only one notification at a time, others may do it differently.
That’s pretty much it. There are some subtleties and variations, but these are the key changes we are proposing, and which we will explore in a netbook device with a partner, as well as in the general Ubuntu 9.04 release, schedule gods being willing.
I think new changes looks more like Growl system used in Mac OS X. You can read more about proposal including mockup video that shows new notification system here.