Quote - As far as I know, you need ray tracing to get the correct angle of the light for SSS. > Quote -

No unless the ray reaching the surface is a reflected or refracted ray.

Quote - Since the IBL picture is put on a simulated ball arround the szene, you do have angle information.

No, you have not. First at all the intensity depend on the angle, as a point in the IBL image can illuminate many objects and points of an object, each direction has other angle and this is not stored in the image.
You must remember that any pixel of the IBL image can iluminate the same point of the object, so the illumination on this point is the integral over all the IBL image that is able to reach this point. This is something that ray tracing don't do. It can work only for perfect mirrors because only one direction is illuminating the point and so only one point of the IBL is taken into account, but fail with surfaces that are not mirrors where all pixels of the images makes the contibution.

Quote - Ray tracing can handle particle systems, which are used to display smoke, fire, clouds, water and other things.

To simulate properly you need a great amount of particles, if you are going to ray trace each particle then the render will never end. Ray tracing can work with systems that use few particles, but for large amount of particles there are other methods.

Quote - If you think scanline is a slow algorythm, as is ray tracing, what kind of algorythm are you comparing ray tracing to?

Scaning polygon by polygon using Z-buffer, no scanlines, in the rendering buffer the polygons appear in their respective position as are rendered.

Quote - Again as far as I know you use the scanline algorytm to fill a Z- or W-Buffer.

Scanline can or not use z-buffer depending on the method used, but if used the z-buffer is for one line scanline and not the whole image..

Stupidity also evolves!