Depends on what you're using bike for too.
MTB gets used offroad (Doh!). I accept it's going to be muddy and I'll end up muddy on it.
Muckynutz. to try and avoid a wet arse and getting a facefull.
Road bike. Nothing. Rarely gotten wet.
Longtail. The utility/shopping/everything else bike. Used year round on roads in all weathers. Full length SKS guards. Even if it's just wet and not actually raining stops me arriving at destination covered in road crud.