We did it some years back. Really bad presentation. I wouldn't personally waste the euros unless that has improved. I picked up most of my historical info digging around before and after the fact.
Here's the deal: we did it strictly for the archeological value: it may originally been constructed as a cistern, and may had an 8th-century B.C. temple in the lowermost level. Around the 4th century BC to 4th century AD or so, it was used as a short-term prison for the almost-certainly condemned: long-term incarceration wasn't a practice in ancient Rome. Prisoners here faced a nasty death via any number of means. Some of the executed were throw off a since-demolished stairway nearby - the Gemonian Stairs - from Capitoline Hill, the bodies were left to decay before being tossed into the Tiber.
But no firm evidence has been found to prove or disprove the legend that either Sts. Peter or Paul were ever held here. That's said, I'll leave it up to you to whether it's something you want to include in your itinerary?