Version 3.0

There was a logic error when prompting the user for the options.  Ignore case value was reversed.

README

@@ -100,7 +100,7 @@ At this point you want to update your Vim syntax file to include all the new met
 
 You cannot run Diff against this, since the lines are completely different, you need to compare the words.
 
-After running :WhatsMissing, you end up with a split buffer showing:
+After running :WhatsMissing, you end up with a split buffer showing (in this case), only the words missing.  This reduces the work required to determine which syntax elements to add to your file.
 ***************
 (19 of 24) items missing from: syntax.vim
 ----------
@@ -127,3 +127,6 @@ varexists
 WMOptions:
 mode=word ignore_case=  ignore_whitespace=0
 ***************
+
+Of course, the above example is for Vim syntax files, but it can be used for anything.
+

plugin/WhatsMissing.vim

@@ -1,15 +1,15 @@
 " WhatMissing.vim - Shows what is missing between 2 buffers
 " ---------------------------------------------------------------
-" Version:  1.00
-" Authors:  David Fishburn <fishburn@ianywhere.com>
-" Last Modified: Sun Oct 17 2004 10:25:19 PM
+" Version:  3.0
+" Authors:  David Fishburn <dfishburn dot vim at gmail dot com>
+" Last Modified: 2012 Jan 22
 " Homepage: http://vim.sourceforge.net/script.php?script_id=1108
 " GetLatestVimScripts: 1108 1 :AutoInstall: WhatsMissing.vim
 
 if exists('g:loaded_whatsmissing') || &cp
     finish
 endif
-let g:loaded_whatsmissing = 100
+let g:loaded_whatsmissing = 20
 
 let s:wm_buffer_lines      = 10
 let s:wm_matching_cnt      = 0
@@ -360,28 +360,29 @@ function! s:WM_SetBufNbr( bufnr )
 endfunction
 
 function! s:WM_SetFileName( filename )
-    if !bufexists(bufnr(a:filename))
-        if filereadable(a:filename)
+    let filename = expand(a:filename)
+    if !bufexists(bufnr(filename))
+        if filereadable(filename)
             " load the file into a new buffer
-            exec 'view ' .  a:filename
-            if bufexists(bufnr(a:filename))
-                let s:wm_find_bufnr = bufnr(a:filename)
+            exec 'view ' .  filename
+            if bufexists(bufnr(filename))
+                let s:wm_find_bufnr = bufnr(filename)
             else
                 call s:WM_WarningMsg(
-                            \ "Failed to load: " . a:filename
+                            \ "Failed to load: " . filename
                             \ )
                 return -1
             endif
         else
             call s:WM_WarningMsg(
-                        \ "Cannot find: " . a:filename
+                        \ "Cannot find: " . filename
                         \ )
             return -1
         endif
     else
-        let s:wm_find_bufnr = bufnr(a:filename)
+        let s:wm_find_bufnr = bufnr(filename)
     endif
-    let s:wm_filename = a:filename
+    let s:wm_filename = filename
 
     return 1
 endfunction
@@ -480,7 +481,7 @@ function! s:WM_PromptOptions()
                 \ response
                 \ )
     let s:wm_ignore_case = (response ==# '1' ? '' : 
-                \ (response ==# '2' ? '\C' : '\c' ) )
+                \ (response ==# '2' ? '\c' : '\C' ) )
 
     " Ignore whitespace
     let response = (s:wm_ignore_whitespace == '' ? '1' : '2' )