Postby Javizy » October 23rd, 2008 4:35 pm
It's limited in the sense that it can only mark yes-no questions. I think it depends on the tone of the speaker as to whether it's soft. You hear people who speak まきじた-style use it all the time, like わかるかい, but I've also heard it used towards somebody who seems upset, like だいじょうぶなのかい. Two completely different ends of the spectrum.
Strictly speaking it is an informal question marker used in male speech, but it's still used by women occasionally. By the way, the non-yes-no equivalent is だい, but I've only seen that used in Doraemon, so I can't really comment.