SJK  > Would it be advantageous for the general user to install this?

Nope.

> Would it enable him to play any unusual formats he may encounter on the web or 'net?

Nope; it's specifically for decoding ProRes, as the DESCRIPTION clearly explains (did you read it?).  
(Version 1.0)

FARDILHA  If you want your Quicktime player to behave as a true Swiss army Knife, you need to install the following (free) extras:

Perian ( http://www.macupdate.com/info.php/id/22923/perian )

• AVI, FLV, and MKV file formats

• MS-MPEG4 v1 & v2, DivX, 3ivX, H.264, FLV1, FSV1, VP6, H263I, VP3, HuffYUV, FFVHuff, MPEG1 & MPEG2 Video, Fraps, Windows Media Audio v1 & v2, Flash ADPCM, Xiph Vorbis (in Matroska), MPEG Layer II Audio

• AVI support for: AAC, AC3 Audio, H.264, MPEG4, and VBR MP3

• Subtitle support for SSA and SRT

Xiph QuickTime Components ( http://www.macupdate.com/info.php/id/20014/xiph-quicktime-components)

• Ogg/Vorbis

Flip4Mac WMV Player

• .wma and .wmv  
(Version 1.0)

FARDILHA  I forget the link for WMV Player: http://www.macupdate.com/info.php/id/17787/flip4mac-wmv-player  
(Version 1.0)

D9  Be careful of Perian. It causes problems for some video players, in particular EyeTV.  
(Version 1.0)

DOM21  Thank you VERY much!!  
(Version 1.0)