I have a Troxel Dakota Duratec and love it! I just started wearing a helmet regularly last fall because I was starting to pony out my colt and I felt that bringing the colt along increased my chances of a wreck.
The only downside is lack of shade. I really need to invest in one of those expensive helmet shades or something, because my face and neck are really burned. I ride almost every day and I don't understand why a helmet can't also give you the shade of a hat.
I really love my Aussie hat. But I love my Troxel helmet too. I wish I could have the best of both worlds- the shade of a western/Aussie hat and the protection of a helmet.
I know they make (or used to make) a western helmet-hat, but I read reviews that said it makes you look like Yosemite Sam- the hat was huge in order to cover the helmet.