The bundled import man page script is very useful, but by importing the pages as text, it does drop keyword (and header) highlighting.
I personally find that speed of visual scanning and comprehension is helped by the highlighting, so I am using a lightly edited version of the script, which imports man pages as PDF files.
-- ADAPTED FROM:
-- Man Page
-- Created by Christian Grunenberg on Sat Apr 16 2005.
-- Copyright (c) 2005-2009. All rights reserved.
-- Edited by Houthakker 2011 Feb 12 to import PDF (rather than text) version of man page
-- (to preserve highlighting of keywords and headers)
tell application id "com.devon-technologies.thinkpro2"
try
repeat
set page to display name editor "Man page" info "Enter the man page to import:"
if page is not "" then exit repeat
end repeat
show progress indicator "Converting man page to PDF ..." steps -1
set strPDF to "~/" & page & ".pdf"
set strCmd to "man -t " & (quoted form of page) & " | pstopdf -i -o " & strPDF
do shell script strCmd
tell application id "com.apple.finder"
set strTmpPath to (((path to home folder) as text) & page & ".pdf")
set blnExists to exists strTmpPath
end tell
if blnExists then
set oRec to import strPDF name page to current group type pdf and postscript
tell application id "com.apple.finder" to delete file strTmpPath
else
error "Page does not exist."
end if
hide progress indicator
on error error_message number error_number
if the error_number is not -128 then display alert "DEVONthink Pro" message error_message as warning
hide progress indicator
end try
end tell