Title says nearly all. - Arts is dead & unmaintained upstream. - Users using it are encouraged not to, unless they really, really have a specific need to use it, at least that's my observation in #gentoo-kde, and on bugzilla. I don't think this should be a default USE flag anymore.
KDE agrees.
Right, but such a change requires a profile update, so we have to wait for the next snapshot.
Shouldn't there be also some default setting or suggestion for an external audio player for KDE notification?
@Vlastimil: As light as we choose it (e.g. sox comes to mind), some people will complain, because it's the /wrong/ player or they do not want one at all. Personally I don't have a preference here. For newbies, who are fond of system sounds, an out-of-the-box-solution is nice. For everyone who cares to read a post install notice, such a notice will suffice.
This is changed in the 2008.0 development profile for x86. As such, I'm marking this as InCVS for now. I'll be creating a patch for other arches.