This is big news for Google Apps. Compliance and archiving are huge concerns for corporate customers. Just ask Intel or Merrill Lynch. Full-blown compliance systems are typically very expensive and come with liability concerns that make choosing a vendor very important. With Google in the game now, it makes the decision to move to a hosted collaboration platform like Google Apps much easier.

Some key features:

Policy management: lets administrators implement rules for how
messages are handled based on the sender, recipient, attachments or
content of the message.

Message recovery: allows you to search for mail across your whole
domain and recover deleted emails on a 90-day rolling basis, adding
peace of mind that important information is safe with Google Apps,
even in the case of accidental deletion by your users.

A full description can be seen here:

http://www.google.com/a/help/intl/en/admins/new.html#admin

the ‘net seems to be buzzing about this a bit:

Information Week

dbTechno

ArsTechnica