Manila can easily redirect weblogs to a new address on another server: All I have to do is edit a line in the config.mainresponder.domains table.
The primary disadvantage to moving is that Manila implements a redirect with an HTTP status code of "302 found," which could indicate a temporary move, rather than "301 moved permanently." A site's Google pagerank isn't transferred with a 302 redirect. I'm hoping that UserLand updates Manila to address this issue.
If you had an old weblog on Buzzword and it's now published elsewhere, let me know and I'll redirect visitors to your new site.