https://steveire.wordpress.com/2011/05/01/it-is-coming/
"KDE PIM 4.6 is due to be released on June 7th alongside the 4.6.4
versions of the rest of the KDE application suite.
In terms of features, we think it is user ready and there have been
many positive reports already from users of development versions. It
is definitely not bug-free however. There are still some problematic
communications with Exchange servers, and some resource usage spikes,
but we are confident that this is overall a step forward. Users will
be able to (mostly) downgrade to KDE PIM 4.4 if the 4.6 version does
not meet expectations, but that is not a long-term solution so good
bug reports will be required for a smoother experience going forward."
-c