I'm actually not really a big fan of the whole rapping thing in pop songs. It's way overdone in k-pop. I'm at least hoping the song is going to be some kind of smooth r&b or funky song.
I have to agree. Not that the korean pop-rap sounds so much alike the western rap i'm used to listening to, but still. Kara did good with Nicole, WG has YooBin. To me that's enough with rapping in girl groups. But of course, if this rapper dude can help them lay down some funky beats, then i'm all for it.
I mean it could very well result in a really sexy video, with ass dropping and minimalistic clothing. Not SNSD's style, but i would not mind some change with one song (+MV of course, duh) like that. 

* Sev watches YoonA's purdy bum shake around