Vista - 2005 xml equality

Is there any (perhaps roundabout) mechanism for testing xml columns
for equality?

Specifically, as part of a bulk update (i.e. into a staging table that
is then migrated) I want to short-circuit any records whose xml hasn't
actually changed, since I have audit requirements and I don't want to
fill in the audit every time a record is present in an extract - only
when it has actually changed.

Any ideas? I have tried a few approaches like extracting as ntext or
some of the checksum functions, but not with any success. CLR perhaps?

Marc