So, good and bad:
1) Blogger extended the cutoff date for FTP support until May 1st. But
2) They put a message at the top of the Dashboard that pretty much said 'fucking get with the program, already.'
So I think the time has come to make the switch. Starting soon - not this weekend, but early next week - the Rambler's new address will be 'www.subway-rambler.copper-man.net'. I have no idea how this will affect those who access these dwindling presumptions and observations via RSS, but just the fact that you use RSS means you know about this stuff and will plan accordingly. Or is that play accordion? I forget.
Supposedly, the migration tool that Google has set up will port not only all the existing entries, but the comments, too - but I apologize in advance if I do something that makes your comments on previous posts go spiraling out into the black haze of the digital void. I actually do really treasure the comments here, and in fact the main reason I haven't yet dealt with the FTP situation is that I was afraid of losing them.
The Blogger migration tool also promises to make sure that all links - internal and external - to individual entries will be automatically redirected when the blog republishes. Which seems pretty magical, to me. They also promised me a pony and a new bicycle, so we'll see just how trustworthy they are. This is Google, after all.
Anyhow, I've gone ahead and called my host and set up the CNAME, so as soon as that resolves (within the next 24 hours), I'll be free to make the change. I will, of course, place a redirect at the Rambler's current address, so you can't miss it.