Well, I just bit the bullet and deleted my Blogger blog. After investigating, trying and actively using WordPress I decided there wasn't much point keeping my other blog up. So it was unceremoniously deleted today. Dead, kaput, gone.
The WordPress categories help organise my posts and the beta 'Tags' in WordPress have already brought more traffic to my site, 2+ visitors vs 1 visitor at Blogger, in a month than the two years I used Blogger.