For some reason ubuntu had a really old version of wanderlust (2.10 series, which is more than two years old). I guess no one updated the debian repository until very recently, so when ubuntu 5.10 came out, it was already too late to get included. Thankfully, the ubuntu universe pool has a .deb for the newest 2.14 series (which was still released 10 months ago!).
They seem to have fixed a number of bugs, including ldap getting stuck sometimes. The LDAP integration in wl is nicer compared to mew, because it doesn’t require a separate module, and TAB looks up LDAP automatically, where as in mew, you’d have to do a separate sequence for the first lookup.
I’ve also figured out how to turn on autofill mode if anyone’s curious:

(add-hook 'wl-draft-mode-hook
          '(lambda () (auto-fill-mode 1)
             ))

My explanation for what this does (according to my simple, yet recently slightly improved understanding of emacs lisp) is, it calls the add-hook function, to add a function to the wl-draft-mode-hook (which is defined by wanderlust). The quoted list beginning with lambda is like an anonymous function (I’m not sure why the first empty list is necessary), but the remaining items in the lambda list get evaluated one after another, in this case (auto-fill-mode 1).
Update
Though I hardly ever use any Japanese at work, I still spent some time trying to figure out if I could type Japanese emails using wanderlust. Emacs has a surprisingly good framework for input methods, and many of the opensource Japanese input methods have emacs lisp plugins for this framework (the package anthy-el in debian/ubuntu for example) So once I got that going, using the emacs with X11 to type in Japanese was no problem.
Through the terminal, was a whole ‘nother ballgame though. Apparently emacs’ support for display CJK characters in a utf-8 terminal is not complete in the 21.x series (though I’ve read that it’s been improved in the 22.x development series). So the solution is to install the mule-ucs emacs lisp package, and then add the following magic to your .emacs file:

(require 'un-define)
;; character encoding
(set-language-environment "UTF-8")
(set-terminal-coding-system 'utf-8)
(set-keyboard-coding-system 'utf-8)
(prefer-coding-system 'utf-8)
(setq erc-default-coding-system 'utf-8)

So that’s fine, and then to get this to work through Terminal.app on OSX, there’s a bit more magic, namely, in Terminal.app’s Window Settings, under Display, you need to check both of the options that begin with “Wide Glyphs …” and also make sure your encoding is set to UTF-8.
Now that all works fine and dandy. I can use anthy-el to use the emacs mechanism to input Japaense, even when I access through Terminal.app.
The only remaining problem is that the client-side mac OS X input method ‘kotoeri’ doesn’t work. If I hit option-space and switch it to Japanese and start typing, I do get the pre-edit buffer, but as soon as I try to commit, emacs chokes. I guess it can’t handle utf-8 coming in as input, though you would think that the (set-keyboard-coding-system) command would make it handle exactly that case.
Oh well, enough for now I guess.