Here are the tags currently used:
<Field Name="Filename">\\RUMPUS\Media\Video\TV Recordings\ANZ Netball Championship 2010-08-10.ts</Field>
<Field Name="Recording Rule ID">572962657</Field>
<Field Name="Stack View">0</Field>
<Field Name="Media Sub Type">TV Show</Field>
<Field Name="Series">Netball</Field>
<Field Name="Name">Test Series: 1st Test</Field>
<Field Name="Genre">TV Recordings</Field>
<Field Name="TV Channel">64156</Field>
<Field Name="Duration">7801</Field>
<Field Name="Playback Info">(1:2)(12:DTVProgramID)(4:1569)(9:CropEdges)(1:1)</Field>
<Field Name="Bitrate">22695</Field>
<Field Name="Stack Top">-1</Field>
<Field Name="Compression">ts video (video: MPEG-2 Video, audio: AC3)</Field>
<Field Name="Date Recorded">40400.6666666666642413</Field>
<Field Name="Keywords">Sports Group</Field>
<Field Name="Access Rating">G</Field>
<Field Name="Description">Netball.</Field>
<Field Name="Artist">ONE HD</Field>
Of these I'm guessing to categorise TV Recordings further you could use:
"Media Sub Type" = currently uses TV Show, but you could have Sport, Kids, etc etc
"Keywords" = I've got ones with Sports Group, Drama, Live, Arts and Livings (so I guess there are heaps more )
"Artist" = Channel Name