This is one of the most fun things I did while in Beirut. Our tour guide was amazing--knowledgable, enthusiastic, and very nice. She was able to answer any questions, and she engaged in some great conversation.
The sites themselves were fascinating. The caves were otherworldly, like nothing I've ever seen. Byblos was steeped in history. There's one tiny shop that sells authentic ancient artifacts for pennies on the dollar. Treat yourself.
Bottom line: This is a great tour and well worth taking.