We've got a few others that seem to be promising PN capability at or near the 3.0 launch, courtesy of reader Joachim's research help: Beejive IM and ngmoco's Touch Pets Dogs. A quick search of Apptism for 'push notifications' reveals a few more candidates, including David Fletcher's ChatMaster. Searching the iTunes Store itself shows a couple more interesting (and not necessarily shipping) apps: speed trap checker Trapster, killer Jabber/XMPP client OneTeam, personal finance tool BillMinder and IT manager's virtual machine toolkit VManage all list PN on the roadmap but no sign of new versions yet.
Once the 3.0 version is released and developers can loose their tongues, we fully expect to hear about scores of updates to take advantage of PN and other new features. If your app is among the revised horde, shoot us a line at our app review address.
Thanks to Will for the suggestion.