I broke down and purchased a handlebar bag in preparation for a 400k in a few weeks. Took it out for a 18 mile spin at lunch, 1000 foot 10% climb with some following fast descents, bumpy roads etc. Moved my light to the fork from the handlebars and it held up well. It's nice to be able to reach in while riding. Only put a few pounds in it, although I tried riding around my neighborhood with a good 12 pounds of rocks in it a few days ago. I'll probably never put over 5-7 pounds of stuff in it though.
I picked the Lone Peak H-100 bag based primarily on a Nick Bull recommendation. 11 liters.
I'm converted. I can't see riding without it. And I clocked my fastest time on the lunch route this year, and it was breezy today.