When I'm on a bike, I honestly don't feel safe taking up the entire lane. I guess in theory the expectation is that cars will calmly drive behind my slow bike until there is room to pass, however long that may be, but I know that people are going to get impatient, and that just makes it feel less safe, or inappropriate. I feel like at any second I'm going to get startled by a loud car horn right behind me, which is very distracting.

So for me the sharrows do make a difference, since they make it feel safe to use more of the road, which makes me do it.