I always try to stick to the road, and obviously the bike lanes where they exist, but there are a few places in my commute where the only safe option is to hop up on the sidewalk for awhile. I know it bothers pedestrians on foot but I'm always super aware of who's coming and going and I only do it when I need to, as well as pulling off to the side to let people pass.
When I'm on foot I don't generally mind if a cyclist is on the sidewalk, but it can get really annoying when there's an open bike lane or a road with very light traffic they could be using. Cyclists in groups on the sidewalk can be particularly frustrating/dangerous, especially if they're not willing to make room or if you've got small children or a stroller with you.
In my neighborhood adult tricycles are becoming really popular, and it's a bit of a conundrum because they literally take up the entire sidewalk and are impossible to get past without stepping into traffic. On the other hand, they don't really seem safe to operate on the road either and look like they would take up too much room on the shoulder.
When you're commuting do you ever ride on the sidewalk or do you try to avoid it?