IIABDFI (If It Ain't Broke...) - nothing in Lollipop is ground-shakingly new or improved and too much reported (and tried at this end) to suggest that an install of Lollipop on an 'older' device will lessen your user experience, if not make it unusable.
Lollipop on devices with it native and preinstalled on an Android device seems much better, but otherwise, why screw with something that is (?) working for you?