Actually the main problem is that icons have to be redrawn for small sizes. It doesn't matter when or with what you do the scaling, SVGs generally just don't scale well to 16x16 type sizes. Jimmac seems these days to draw icons by hand in the Gimp for small sizes, and then provide an SVG as well for larger sizes.

Precisely. Loading times should be a non-issue, completely. (I will be surprised if profiling shows icon loading as even a significant portion of the startup time.) The fact is vectors loose crispness at smaller scales.

Ashwin