It looks as if Word Press will be releasing version 2.9 soon. So I will hold off for now updating the blogging software.
I may yet shut down comments until the update is installed, to ward off spammers. But for now I am leaving them open. Bulk-deletion is annoying, but not all that difficult, as long as the filter keeps holding the spam in moderation rather than letting even a small percentage of it to sprout in the orchard (as had been the case till yesterday when I adjusted some settings).