There's a plan currently under discussion for bus rapid transit on the Geary corridor, which is sort of the el-cheapo version of that idea (http://www.sfcta.org/content/view/37/70/). Give the bus a dedicated, physically separated lane to reduce traffic problems, and build light-rail-esque, less frequent stations in the median with level boarding. Not a full solution, but the hope is that it'll raise the average bus speed significantly.