Not on my work commute, but on my "errand" commute to stores a half mile away I use sidewalks for two short sections on the return trip because it's just much safer (Intersection of Commonwealth Ave & Chestnut Hill Ave in Boston). It's 4 lanes of traffic intersecting 6 lanes of traffic with treacherous trolley tracks in 3 of the 4 directions. Getting down to the stores is no problem on the road, but getting back in traffic *and* making sure to cross all track and track intersections at 90 degree angles is just about impossible unless I use the sidewalks. Just be courteous to pedestrians and slow to their pace if there is no safe way to pass.