Both the update (11.2.3) and e2sync enable Entourage to work with OS X sync services. But I’ve found the third party tool a somewhat buggy way to achieve this essential function.
Of course, I don’t actually know Microsoft’s solution will be better, I’m just downloading it now. I’ll post my findings!
Update: It’s beautiful. When you’ve installed the update, go to Preferences in Entourage and you’ll find new Sync Services and Spotlight preference options. For Sync Services, you can choose which Entourage calendars/contacts to sync. I strongly recommend you don’t try and merge these – I got into all sorts of trouble with this because I’d already been syncing them with e2sync so everything got duplicated.
In iCal, Entourage creates a calendar called Entourage, whose description tells you “This calendar is automatically created by Microsoft Entourage”. Any changes in this calendar are reflected in Entourage and visa versa – which is a nice, simple approach – and appear almost straight away, so no messing about with iSync, which is beautiful.