This is also one of my faves as it shows abundant detail in my smallish scopes. Dubbed the swan nebula and also the omega nebula it sure does look like its name sake. I have even heard someone call it the NIKE checkmark
And it sure does look like a checkmark in my 10x50's. This one benefits greatly from the use of a nebular filter (like my Lumicon UHC) but looks pretty even without the filter. With the nebular filter in place the swan takes on a feathery look with nebulosity "billowing" from the swans back. Also the region seperating the neck from the back and also the front of the swan's neck and head look very dark and more pronounced with the UHC in. I can also detect extended nebulosity around the swan with the UHC (first noticed this in David westsky's 10" and later looked out for it in my 6"). I have a more recent updated sketch that I will upload later. For now see:
http://www.geocities.com/dhumpie/dastro/m17.jpg
Darren