Since http://en.wikipedia.org/ is arguably a better URL for linking to the English Wikipedia main page than http://en.wikipedia.org/wiki/Main_Page, I'd see no reason not to make the redirect a 302. We'd just be telling visitors that "our main page is over there, but feel free to keep using this shorter URL".
Right on! (1960's language)
T> http://en.wikipedia.org/wiki/Main_Page just looks ugly
And don't forget those of us who prefer to configure our sites with genuine index.php URLs.
$ HEAD -dSP http://transgender-taiwan.org/ HEAD http://transgender-taiwan.org/ --> 301 Moved Permanently HEAD http://transgender-taiwan.org/index.php?title=%E9%A6%96%E9%A0%81 --> 200 OK
What this says is that all webmasters who link to the former tidy URL, should instead change that to the latter blathersome URL. Fat chance they would say, especially if the were the Dmoz indexers, etc. "Come back when your site is fixed".