VIZ alters the sound effects instead of leaving the original ones with notes at the end like Tokyopop does. I prefer that the sound effects aren't translated into English with notes. My reason for this is because we lose some of story occasionally when the sound effects change. Though personally I'd prefer it if the sound effects were both in English and Japanese on the same page, either next to the sound effect or a note on the bottom of the page.
For example, Laughter in Japanese depending on which way they decide to do it tells us more about the situation/person.
ahaha = laughter (see also ha ha ha for masculine laughter, and ho ho ho for refined feminine laughter)
bwahaha = evil laugh, same as fwahaha, gahaha, gwahaha
fu fu fu (hu hu hu) = a strange laugh. M.J.: "The evil chuckle in the back of the throat." (see also ku ku ku, pu pu pu)
he he he = heh heh heh (laugh)
Here is a page on Japanese sound effects and what they mean.
This Battle Angel Alita (Gunnm) Last order website can teach you enough of the basics of Japanese kana to understand some of the sound effects found in manga.