http://forums.steampowered.com/forums/showpost.php?p=34032703&postcount=68
"Validating files" every time should be fixed by this change.
We'll migrate certain user config files to the new directory when the real game is converted. (But probably not custom content. That will just stay in the old folder and you can move it to the appropriate place.) We didn't do that for the TF beta, though. We'll have a blog post that explains more details about that when the time comes.
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Users of the TF beta are reporting their boot and load times have been cut in half.
Good news