If you have deployed or are in the middle of a MOSS deployment, SP1 should be of major interest to you. It addresses many of the product issues that your team may have realized during the implementation/configuration of the platform.
Personally I have experienced two issues which would be resolved by SP1:
- Editing of documents crashes with multiple versions of Office installed
- Send to Link in the context menu of the document mutilates the link in the email body
For more information, please refer to the MS Sharepoint Blog
Service Packs have been released moments ago and you can now download WSS SP1 here & MOSS SP1 here.