As we have all learned, Attached or overlays are required for different purposes. The safer way is to use overlays. As for the comment about circular reference being resolved in r14, I had a problem just yesterday with this in 2002 files.
Attach will work well for certain situations where you don't want to keep referenceing the same set of drawings over and over again. Instead reference one file with all your reference's attached.
If you work with background files for different disciplines or parts of a job and you have 20-80 background files. If one file has all 80 attached in, where ever that one file get's referenced in, all 80 will follow. This may not be effecient because you only needed to show 5 of the 80. Overlay would not allow the 80 to follow.
One thing that I have done in the past is create a referencing file. This file is a blank file with nothing but reference files attached. You can then use this file to populate your drawings with your normal set of files that need to be referenced in... your background files can still have reference's that are overlayed...
Pieter