I like mine at 725mm. I still have some uncut 780 and 800mm bars on a couple of bikes; I find them too wide, but those are on low-mileage bikes so don't bother cutting them.
Many bars come with marks to make cutting down to the width of your choice easy.
My olde Bridgestone came stock with 22.5" bars - insane! Ye olde Klein has 23" bars - still too skinny.