Btw, for such simple re-colouring I'd probably rather used CSS hue shift filter or similar effect, and kept the SVG "dumb". But for having different shapes or geometric properties this approach is indeed nifty.
Yes, I do that, too. The benefit of using the sprite system is that it's pretty general, so once you have some CSS for it, it's easy to keep adding new icons. CSS filters are usually more special for each case, but I use them too (mostly for brightness and greyscale things that are repeated on multiple places, e.g. tabs or disabled state).
