Plastic sheets for window insulation: any comments and experience to share?

A member of my household is pushing for installation. Should I overcome my resistance?

• Once in place, are they ugly?—a sheet of plastic across the whole window opening?
• Are they a pain in the neck to remove cleanly when the weather gets warmer?
• Do they cause any problems in themselves?
• What about with pets?
• Do they work as advertised?

I’ve seen the manufacturer’s installation video and a removal video and looked at Amazon customer reviews. I’d like some independent and unpaid reports.