The modern slice is a bit different than the shot that Rosewall hit. The modern slice has both back and side spin (in varying amounts). It has good pace (for a slice), stays low, can have a lot of curve, and you're never quite sure when it's going to finally land and bounce. The biggest downside is that you have to get it low over the net, so there's not a lot of margin.
Here's a good tutorial on the modern slice: http://www.youtube.com/watch?v=II7Wo0y6fC8