Six days later, I have: three empty inboxes (work, Debian, and personal); one mailbox containing what used to be in my inbox, from which I've archived about 2500 mails elsewhere; one to-do (or "to reply to") mailbox with five items in it; and some happy people with prompt replies from me. Moving my old inbox aside would achieve nothing if I weren't dealing with new things coming in or making progress with its former contents, so this seems like a pretty good result so far.
Thing I haven't got right so far: I'm now checking my e-mail too often because the inbox is so shiny and clean that I can't quite get over it. :-) I'm spending next week in London, so that should forcibly help me out of that habit.
Thing I don't like about Inbox Zero (but fortunately is a non-essential component): the recommendation to use very few archive folders. Aside from not especially liking the idea of relinquishing all my mail to Gmail, I find that I'm much more likely to be able reliably to identify the topic identifying its folder (and then maybe to pare that down by sender or something) than I am to be able to identify a halfway-useful set of search terms. If I went back and labelled everything to match my topic-based folders then I might be able to use a single archive folder, but I don't really see the value in bothering with that. I don't often find myself spending much time searching archive folders, and when I do it's usually when I'm running statistics on things like bug folders. I'll ignore this bit unless and until it becomes a problem.
Edit: Which all means "if you've sent me personal mail expecting a reply and I haven't replied to it yet, I probably won't, so please resend it".