Dinesh just posted a list on the forum of the key changes which will occur between Beta 2 and RTM for Linq to SQL.
Read them here:
Main changes are renaming of the Add/Remove methods to make them more descriptive. They will now be called InsertOnSubmit() and DeleteOnSubmit().
The OnValidate() method will now have a ChangeAction value so you know if your validating a delete, insert or update. This will be very useful.
One thing mentioned which was interesting is that the next release will be RTM and they are skipping RC. Tiscali (ADSL provider at the moment) will be happy…