See coverage about this from:
BoingBoing.net: Danger to Mac Users "Eat Sh*t and Die"
Engdaget.com: No Mac Sync for SideKick II
If I read all this correctly, Mac users who buy a SideKick have no way to export their contacts from the SideKick and, even though some enterprising developers did the work for them to make their platform compatible with iSync, they refuse to make the software available to end-users. Yeah, well, I'll stick to my very capable Sony Ericsson t610 for now.