I don't even use Word or anything similar to write in English. BBEdit is my tool of choice. Most of my writing seems to be for emails or online use and is fairly short; who needs to deal with the bloat of Word when you just want to type some paragraphs?
If I do feel I need things like furigana or top to bottom left to right formatting I use LightWay Text. This is a small word processor that reminds me of MacWrite II, but as it is written by a Japanese developer it has Japanese features. And if you want you can run it in Japanese. It actually works a bit better in the Japanese version.
And I got a nice thank you from Itoh Yumiko-san when I registered. (Bill Gates doesn't send me email, but then I don't have any MS products anymore).
Another useful feature is a template for Japanese squared manuscript paper that I can print out to practice handwriting.
It runs on Windows and Mac.
The only minus is that the English version doesn't handle file naming in Japanese and you get mojibake.
Mail on the Mac always gave me problems with encoding, as 2002-JP seemed to be the better choice rather than UTF if I wanted it to be easily read. So I went for the simpler, but better for me, GyazMail. Again a Japanese developer so maybe that's why it did what I wanted. (I tried every mail program I could find before opting for GyazMail. )
LightWay Text (Japanese)
http://homepage1.nifty.com/lightway/
LightWay Text (English, French, Italian)
http://members.aol.com/LightWayText/
Gyazmail
http://www.gyazsquare.com/
What I really want is some better Japanese fonts.
Expensive when you consider the amount of work involved to make a full font. I think maybe there is a little less room for weird fonts as the kanji quickly become unintelligible.
Have you found Maniackers? Mostly kana fonts unfortunatly mapped to keyboard so kotoeri doesn't work with them.
http://www2.wind.ne.jp/maniackers/designfont.html
Mikachan. A complete handwritten font
http://www001.upp.so-net.ne.jp/mikachan/
Kouzan mountain font.
Not 100% sure of the terms of use with this font. It's in Japanese, but from what I can make out its free 無料 and presented to the public 公開.
http://musashi.or.tv/aoyagikouzanfont.htm
And a large listing in Japanese of free fonts, mainly for PC and many seem to be partial sets.
http://www.akibatec.net/freefont/
And commercial fonts listings and a good free font listing.
http://ohkadesign.cool.ne.jp/wabunfont/index.html