Here are some things brought out in the document:

• Custom Weighting feature for IMF -  If you want to tweak the rules for the IMF to better fit your organization, you can do it using MSExchange.UCEContent.Filter.xml.  For example, if you are a company that uses the word “Foo” a lot in your emails and you want to be sure that all emails with the word “Foo” in the subject be let through no matter if it might be spam or not you can add the line:
  <CustomWeightEntry Type=”SUBJECT” Change=”MIN” Text=”Foo”/> 
  This will lower the SCL rating to the lowest it can be (0) so that it should pass through.  You can choose words in the body, the subject, or both.  You can also choose to increase the SCL.  Increasing the SCL could be useful in instances where you need to make sure that all mail with “bad words” don’t get through.  Here is a tip:  Use notepad.exe to create the file and make sure you save the file in UNICODE format.
• IMF v2 vs. IMF v1 – If you are running the original IMF (v1) on the server that you are installing you will need to uninstall it before you install SP2.  This is because IMF v2 is installed with SP2.  You will still need to enable the Intelligent Message Filtering on the SMTP Virtual Server.
• Who deleted my Public Folder? - We now can tell you who it was, but you will need to turn up logging before it gets deleted.  Turn logging up to Medium on MSExchangeIS \ Public Folders \ General.
• Disabling MAPI access for mailboxes – If you have a user that shouldn’t be using MAPI to access the server, you can prevent this on a per-user basis.  You can also prevent users from accessing their mailbox if they are not in cached mode.
• Public Folder Storms – Now you can pause and resume all replication of public folders.

This is really just a small part of the great information in the release notes.  I strongly encourage you to read it because it is a interesting read.