Apparently, the export file doesn't contain the category descriptions. After importing it (from v2.5.1 to v2.5.1), the category names are there, but no descriptions. That's disheartening, because I had nearly 200 of them.
Also, I noticed that 20 categories were duped, from sub-sub cats to parent cats, and the posts reassigned to the dupes. Strange behavior for export/import!
What can I do now? I backed everything up, of course, but my Fantastico-created new WP has a different database name from my old one (i.e., I changed to a different server).