Thanks for the character replacement option.
In the attached example I'm set up to append Firefox and Apr 2013 to the file name.
In the file naming template I have name as %filememo%
and comment as
in Automatic Captions I have %description% %customdate% %browserurl%
Previously, if I entered Post Pop Up Working Fine in the post-capture comment field I'd have had Post_Pop_Up_Working_fine as the first part of the file name. Now, I elected to use a space, so that's great for the Post Pop Up Working Fine part but it's not extending to cover the _Firefox__Apr 2013 part (my custom date is %b %Y, btw).
Also, it would be a cherry on top of the icing on the cake if multiple consecutive char replacements could be condensed into just a single item (see the double underscore between Firefox and Apr).
So, in my example I'd like no underscores at all in the file name and only single spaces.
At the moment, the final file name is
Post Pop Up Working Fine_Firefox__Apr 2013.png
I'd prefer to see
Post Pop Up Working Fine Firefox Apr 2013.png