Any thoughts on this oft-overlooked accessory?

For me, I've worn them as a kerchief (folded to a triangle and worn tied over the head and knotted at the nape of the neck) since I started growing out the hair, oh, eons ago, a habit I picked up from my long-haired mom.  They do wonders keeping errant strands from blowing into the face and covering up greasy roots when you're giving it that one more day before washing.

It goes great over a bun for yardwork and protects the hair from the sun and wind (and beach salt too ).  It looks adorable with any length of pigtails or loose hair, and can be dressed up or down depending on the cloth used. 

They're easy to make if you find fabric you like.   Take one you really like as a pattern and chop away, finishing the edge with either a rolled hem, or with pinking shears (those zig-zag scissors) and fray check.  Filmy scarves can look really nice with dressed and fancier clothing.

One problem I've had is keeping them from slipping back on the head.  Generally clipping them above each ear with two crossed bobbie pins or one of those snapping metal barrettes solves that, or wearing your pigtails forward enough to push the kerchief forward.  The barrettes can be fun - I've got a whole box full to coordinate and match my huge bandana collection.

A scarf/bandana also works well UNDER a hat (or in my case, biking helmet).  The scarf protects the hair from any damage the hat or helmet might cause and keeps the hair under control.

Edited to correct silly misspelling 

I'm a bandana banana bwhahaha

Really, I can't say enough praise on the banana. I mean bandana. They were my sole accessory over the summer, especially with weekend trips back home to visit the relatives. Those were the days of minimal packing. Hear hear, let's welcome summer back again!
(1) pj's (2) minimal snackage (3) 1 shirt (4) undies and 1 pair of socks. (5) toothbrush
(6) a bandana
The really cool thing about the usual bandana size is that you can make a regular bun, then cover your head completely with the bandana if you do it right. Fold the bandana diagonally, but not completely corner to corner.

but instead, make the North corners not meet exactly. The top layer may be 3 inches "below" the bottom layer. Put it on your head, as if you were going to tie the bandana back. Actually, you will. But the extension you've created.. will allow one of the corners to be tucked back behind the knot. This is confusing, I might have to post photos sometime.

ETA: AH HAH! Found a website.
http://www.alopeciaboy.net/Bandanas.html

It's kind of like those instructions, only with less tail. Well, if you're covering a bun, then there won't be enough tail to remain anyway.

I find if I keep the front top of the bandana forward  rather than back on my hairline it won't slip off. I usually wear it just half a centimetre infront of my hairline, though if I do wear it further back I'll use a fey bobby pins. 
what is also good is what I wear for medieval reinactment.  It's a type of veil, basically like a very long head scarf.  It needs to be wide enough to go over tyour head and tie underneath, which is the first thing you do.  Its length needs to be longer than your hair, though can be much longer.  with this length draping down your back, you wrap and tist it around your hair and coil it on your head, and it just tucks into place and will stay there. if you have more material than hair you just continue twsting the material.

This is great if you're doing a big spring cleanout or something, cos it will keep your hair clean and out of whatever you're doing.

Oooh, scarf bun is a big success.  Filmier ones tend to fall off, but with a bandana, I don't even need pins.  It works great for overnight conditioner soaks - I slathered the ends in Aubrey Organics for dry/ frizzy hair, covered it with a baggie, then tied a bandanna over it to hold the lot, leaving it loose enough to sleep in. 

Result: No conditioner on the pillow, no greasy scalp, and LOVELY soft hair.