Our early experience with Site Variations involved some nasty errors that were fixed by http://support.microsoft.com/kb/936867 .
Recently we decided the time was right to install WSS SP1 and MOSS SP1. So, the test environment got service packed first. Imagine my surprise when the error from several months ago suddenly re-appeared;
Violation of PRIMARY KEY constraint 'PK__#ExportObjects____########'. Cannot insert duplicate key in object 'dbo.#ExportObjects'. The statement has been terminated.
It seems that the fix we had had to apply has been removed by Service Pack 1, and we're back to having problems. No matter how smoothly Variations seem to be going there always manages to be something of a sting in the tail.
Luckily, the decision to apply SP1 in April 2008 rather than December 2007 has payed off. Others have experienced the pain first - poor trusting fools ;) I knew that being totally jaded after years in the IT industry would pay off somehow - it stops me being gung-ho about installing service packs.
The forum posts above details a new hotfix that you need to install post-SP1 to re-fix your variations.