Well, the thing I'm worried about is that a .XLS extension signifies that a file is an Excel spreadsheet, which means a binary file with a format specific to Excel. I know, I'm being picky.

>>Mark,
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>>Thanks for the reply. I'll have to think about this. I'm not sure I like the idea of giving a text file the extension of .XLS, when it's not really an Excel spreadsheet.
>
>I don't think you have anything to be concerned about. Try it. Do a copy to somefile.xls delimited with tab and then try doubleclicking it in Excel. It opens perfectly fine.
>
>Hm. Are you concerned about really old versions of Excel? I have the luxury of supporting at least office 97.