Meh. We have used it for a while. The format itself is not particularly bad (although it's a bit fat) but the browser support is rather mediocre. For example, neither Webkit nor Firefox will do vector transformations if you apply CSS transformations on the SVG. Instead, they will do crappy raster transformations. And the rendering speed is so slow it's not even funny. So we just switched back to PNG for the time being. Maybe it will get better in a year or two.