I'm confused? Is it worth what? It's free and it lets you bypass the visitor queue! What could be more simple?
When you arrive you look for the designated immigration counter which has a sign for HKIA Frequent Visitor Card above it. There willl normally be a person who will check your card and then you proceed to the counter (or occasionally a queue of 1 or 2 people). This must be better than waiting in line for 10-15 minutes with other visitors. The procedure is the same outbound.
But surely your card came with instructions?