OK. Most important 'joy' in worship is that joy that comes from being in God's presence.
But important joys come from the service of worship being well performed. (By contrast think about the anti-joys that come when the sould system coughs, rattles and booms, or the dignity of the service is destroyed by some crass action or crudity invoked in the course of someone speaking).
Two joys noticed recently by me have been intelligently led, well crafted intercessions.