How do I get all my ID3 ratings into iTunes?

iTunes maintains its ratings and play counts independently of the tags and doesn't read or write to the ID3 ratings properties. There is probably a way of using a 3rd party tag editor to copy the information to a field that is exposed in the iTunes script interface, and then an iTunes script to copy that data into the iTunes rating property. I'm not aware of any off the shelf solution however.

tt2

Reasons for not storing ratings in the files probably include allowing multiple users to share media without being affected by each others changes and to cut down on the file writes that take place. For example with a synced library you can update ratings in either your library or on an iPod and the ratings can get updated back and forth without needing to overwrite the media as it stays unchanged. As I recall WMP will optionally store ratings in files but I think it might do internally for preference.

If you can find a tag editor that can read the rating values then you could just copy them into say the Grouping field. Once the values are visible in iTunes you could sort on them and quickly set all the ratings by hand in 5 or 10 operations depending on whether or not you've used half-stars.

tt2