While tryning to overcome some focus problems I found that some kwin global shortcuts are not working at all.
(some of) these are:

Meta+F5 = Move Mouse to Focus
Meta+F6 = Move Mouse to Center

Maybe some other shortcuts are not working, I just took a quick look at it.
Can someone confirm the issue?

Is this new since you installed 4.8? I'm on 4.7.4 (also with Kubuntu Oneiric) and Meta+F6 = Move Mouse to Center works fine for me. Meta+F5 = Move Mouse to Focus seems only to move the mouse to the top left of the screen - but I have not used it before.

I have a problem with the shortcut for "Activate Application Launcher Menu Widget" not working (whatever I set it to - have tried various key combinations), as of about a week ago ... but I suspect this was about the time I installed some Xfce packages.

On my KDE Trunk system Meta + F6 worked.

So it seems these are problems related to multimonitor (single screen w/ three or more displays) implementation in kde/plasma.
On the same system with only one or two displays it works as expeted whereas with three displays I've found that disabling and then reenabling one of the three outputs let the shortcuts run again. Anyway these are useless since they work in relation to the screen as a whole and not in relation to each display.

While writing this I've also found that any manually added plasma shortcut is not working at all.
Tomorrow I'll try this on another system with a similar configuration.

@Secretcode: I had these problems in 4.7.4 and yes, application launcher menu widget is not triggered here also. Only lancelot is correctly triggered via "alt+F5".