My very first Boss pedal I ever owned and I love it. On my compact pedalboard I can't have an OD and distortion, its a handy pedal to have.
Most of the times I only use the OD, some people say 100% OD or distortion gets a little thin, but I like it. For straightforward dirt I use the OS-2, but for weirder stuff I use the Fuzz Factory, or both.