Mike, it depends on what you define as hassle. If you put in the used bars, get it alinged, and find out later they are sagged, you'll have to get it realigned when you purchase new bars. Bars can be worn but show no signs of fatigue before installing.
One thing to look out for - if, when setting ride height, you have to drive one adjusting screw a lot further in then the other, then the bar you had to drive the screw further on is fatigued. Its normal to have a little bit of difference between the adjustment screws, but, for instance, when I reused my old bars, the left side had quite a bit of thread exposed but right side was nearly bottomed out. That bar had so much preload on it from the adjustment screw that it even had a gentle arch to it
