simon and KDE backward compatibility has always been an issue. Because I use KDE/trunk to develop simon, I tend to use new classes as they appear.
However, OpenSUSE still has KDE 4.2 only in the factory respository and *buntu 8.10 only has it in its backports repository from jaunty.
So while we will not support 4.0 (Ubuntu Hardy), we decided support KDE >= 4.1. This means that users of all major distributions should have no problem installing simon 0.2.