IBM’s recent press release on Viper says:
Viper is expected to be the only database product able to seamlessly manage both conventional relational data and pure XML data without requiring the XML data to be reformatted or placed into a large object within the database.
That, so far as I know, is true, at least among major products.
I’m willing to apply the “native” label to Microsoft’s implementation anyway, because conceptually there’s little or no necessary performance difference between their approach and IBM’s. (Dang. I thought I posted more details on that months ago. I need to remedy the lack soon.)
As for Oracle — well, right now Oracle has a bit of a competitive problem …