Since yesterday evening the openSUSE KDE4:Unstable repositories contains the KDE SC 4.5 rc1 packages. Also the special repository that contains KDEPIM 4.5 snapshots, was updated to a version that seems to work pretty well.
I am not using IMAP, so I can’t comment on it’s status. But the POP accounts are working very well and also filtering is active. At least it allowed me to move away again from Thunderbird to this Kmail v2 solution. A very good job done by the KDEPIM developers!!