This is a version of sed based on GNU sed. It is not a version of
GNU sed, though.

There are several new features (including in-place editing of files,
extended regular expression syntax and a few new commands) and some
bug fixes; see the NEWS file for a brief summary and the ChangeLog
for more detailed descriptions of changes.

The biggest note, i think is the *huge* speed difference, where
regular sed might take a few mins, super-sed can take only seconds
this is not true in all cases, and sometimes you have modify your
regexp syntax, however for the speed increase, it might be worth
it.

WWW: http://sed.sourceforge.net/grabbag/ssed/