So for not, I went and used the strings function to handle binary
files.  that is, I added this line to my swish.conf:

 FileFilter ".xls" strings

Thought I'd still like to know if this is expected behavior.

However, now I have run into a new issue.  I have a unicode text file on
my website and when swish-e tried to index that file, it complained:

Warning: Possible embedded null in file
'/www/html/specs/frankblack/SpecSettingsFiles/reference/encodingsession.txt'

The file is a Unicode format.  I think UTF16.

Since I don't have many of these files, I can change the extension but
it would be nice if swish-e understood Unicode.  I guess I could find
some Unicode to ascii converter and use that in the FileFilter
directive...

I'd be happy to enter a bug report and supply repro (and sample files)
if needed.

thx,
steve