Well... my girls actually had a pair of these!! (They were proper "Wrangler" ones - a gift from some very country friends).
I found them fabulous in our heat to pop over the nappy with just a little lightweight swing top or dress.
If the girls were in disposable nappies I always popped something over for when we went out, if they were in their gorgeous modern cloth nappies, well the whole world could see them!
And at home - just a nappy was totally ok with me in our summers.