I cannot check this, but http://en.wikipedia.org/wiki/VCard#vCard_extensions seems to indicate that is for alternative Japanese spellings, not for truely phonetic entries. If it is for phonetic entries, I would expect that one would have to use the international phonetic alphabet for entries there.

The phonetic field is for Japanese names (at least, that's what Android phones do), where it's impossible to intelligently sort by the kanji name, so you have to enter a kana name as well.

I did try it, but it doesn't seem to make a difference. I might need to test it out more, though.

Set a nickname, that works from my testing.