[gales]

There are icons in the SVG sprite set which consist of numerous clip paths, which could be the root cause of the performance issue. If you load the sprite in Chrome (http://adrianosmond.com/images/sprite.svg) and inspect the element immediately above the facebook logo you will see an example of this. That aforementioned icon could possibly have been created using a single line path and gradient fill (I've not edited SVG files for a while).

[ygra]

You cannot have a gradient following a curve. At least not yet. You could probably use some filter trickery and thus create a fill where a gradient follows the path but I bet that's much worse than a few dozen paths.