I worked for SF for several years (not there any longer).
You're going to find varying opinions based on experiences that people have had with claims, however, even after leaving the company to work elsewhere I would still recommend them.
SF is a mutual company, where as companies like Allstate are publically owned. This means that they are owned by their policy holders, so if they have a good year, and make money, they return that profit to the people who have insurance with them. If a publically owned company has a good year, they return the profit to their shareholders, not the people who have insurance with them.
They are also very good to their employees, which speaks highly of any company. If they are good to their employees, then they are typically good to their customers.