How to regenerate random smart playlist in iTunes 11

I'm not much of an AppleScripter, so this is modified from some scripts at Doug's AppleScripts website, but it's GPLed, so derivative works are allowed as long as they're also GPLed.

My idea was to make a script that could take the release date, which can't be used in smart playlists, and store it in the last skipped date, which can be used in smart playlists. If you just want to do this for podcasts (not for songs, for which you might actually use the last skipped field), just select your podcasts before running this script.

Once you do that, you can create a smart playlist selected on the "Last skipped" field to get the recently released podcasts.

So here we go:

 (*
 You can rename this script to whatever you want
 but please keep this information intact. Thanks.

 This program is free software released "as-is"; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.

 This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.

 Get a copy of the GNU General Public License by writing to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.

 or visit http://www.gnu.org/copyleft/gpl.html

 *)

 tell application "iTunes"
set sel to selection
if sel is not {} then
    set ofi to fixed indexing
    set fixed indexing to true
    repeat with thisTrack in sel
        set reld to release date of thisTrack
        tell thisTrack to set skipped date to reld
    end repeat
    set fixed indexing to ofi
else
    display dialog return & "Select some tracks first..." buttons {"Cancel"} default button 1 with icon 0 giving up after 15
    return
end if -- no sel    
 end tell

New playlists use the current columns in the main music list. If you want to remove those columns, just remove them from the main browsing window (Music under LIBRARY). Then create a new playlist and you should see the new columns appear.