The comfort of a blanket without looking like a burrito.
Transition to the mode that best fits the occasion. If it's sweatshirt time, pull up the bottom elastic band and put it in regular hoodie mode (it holds the bottom portion up and hidden until you need it). When it's chilly and time to cozy up, deploy the bottom portion by loosening the elastic waistband down to your ankles and go full length.
The IWOM easily rolls into its self contained stretch pouch for fanny pack mode wear or easy storage.
Perfect amount of stretch for walking and the perfect amount of hold for when the bottom leg coverage is held up and hidden when you don't need it.