Reflex is part of the bow's geometric design. A bow can either be reflex, deflex or straight and that is principally determined by where the grip is in relation to where the limbs meet the limb pockets. If the grip is closer to the string then the bow is of a reflex design. More reflex usually means a longer power stroke and a shorter brace height (not counting parallel limb bows) which in turn means more speed.

Is it good to have a higher amount of reflex? Yes in that it can potentially offer you more speed when coupled with a shorter brace height. No, in that it can make the bow more critical to shoot.