Pros - Blocks wind, rain,bugs, rocks and extra storage or speaker location. Con - blocks the wind on hot days. I really like mine. On my previous SG I bought the quick release kit and only took them off when I sold the bike.
I've had them on my last two Streetglides. I like the additional storage and wind blockage. They're also extra protection when riding in the rain and-for others (not me), a place for extra speakers!