My wife likes her chain guard, me, not so much.
I have single-speeded both our bikes, her's a '62 Raleigh ladies Sports, mine a India-Hercules sports-clone. Her's is all steel, where mine is converted to all alloy components. I don't know what steel the Hercules made of, but it is lighter than her Sports frame, and is very resilient.
I know I've mentioned it before, but it is flat as a pancake here in our town, and single-speeding makes a simple bike simpler.