I have parted with alu handlebars a number of years ago. I had problems with the bars rotating inside the stem clamp during rough riding. The tightening did not seem to help. After a closer examination, I realized that the handlebar was caving in in the clamp area. My conclusion was that the material was too crummy for the application and live with steel handlebars ever after. The only problem is that right now you get more variations in alu than steel. Since the handlebar-stem combination I have suits me reasonably well, it is OK.