I have fitted mud guards, loads of people either dont bother or have the plastic temp mud guards.
I cant see the point of the temp ones, they're useless, might as well not bother.
A good front guard will keep road grit out of your chain, a good rear guard will stop SBS.
You really notice the difference when riding behind a bike that doesnt have mud guards, you get a load of spray in your face.
I don't have mudguards because I don't mind getting my bum wet. If it's raining, you're going to get anyway. Overshoes, I would wear them next winter because I don't like wet feet.