The added benefit of wearing a schemagh over your hoodie like a belt is that you help trap heat near your core, even while moving around. I wore a schemagh with my wool shirt in this manner all week at Wintercount (very rainy and chilly all week) and didn't feel cold once.
I wear them occasionally, and always have one in any sort of bag I'm carrying. They're useful, but I don't find them to be as useful/convenient with long hair. I wish I could do some of those proper tacticool looking wraps I see, but alas, to carry a mouth as big as mine you've got to have a big head. Too much surface area to wrap around five times, knot three times, use the ends to tie your shoes, or whatever else they've got in the instructions.
I am in. I have a few in my possession. Generally only use them when away from Sheeple. I do what it takes to blend/grey man at all times. Folks in my small town world think a shemagh is only worn by terrorists. (These are the same folks that spend their free time looking for Sasquatch and end up in tornado news clips..."It sounded just like a train!") My go-to pack has one in it at all times. Have used it in numerous ways, mostly listed in previous posts of this thread. If you are looking for 'operator' status, the shemagh will complement your woolly beard and 5.11 pack well. If you are looking for a good piece of lightweight and inexpensive gear for your bag, try one out.
I have a couple of these, one from Black Willow. They are handy for lots of things. I keep one in my hunting pack and one in my hiking pack.
I like to use mine for belt (copied @calebo), head cover over my hat for shade. Recently used as a veil in south Georgia to help keep gnats out of my eyes and ears. I also used it as a tarp sun shade rigged between tree branches during the Idaho bushcraft class. About to replace it with a jumbo bandanna thing that's a solid color just cause I am not cool enough for that tactical guy pattern stuff.
I obviously go everywhere with one of my shemaghs. For my area I like the ATACS-FG shemagh. For those in hot areas you can wet it, ring it out, and then wear it like a "cool" rag as the cotton will make you a walking wet bulb. They're also very warm in the winter so I wear them as a neck gaiter. Extremely versatile piece of kit to have at all times. I even tore one into strips at a 3 car crash to bandage a womans head so blood and glass didn't get into her eyes.