My adult son and I took it yesterday morning and I enjoyed it, immensely.
Seeing Main Street with almost no traffic is really a sight to see, especially when you stop there for water towards the end of the tour and wonder how that many people got there so quickly. The tour itself I found interesting due to my interest in steam trains. My son is not as interested so it probably wasn't as interesting to him. The CM who led the tour was Joe, a long time WDW RR employee, and he was REALLY good. I imagine that which CM you get would make a difference in the quality of the tour.
The tour itself takes you to the roundhouse, which is actually rectangular at WDW, but not inside it due to insurance regulations. Still, you can see the scale of operations it takes to keep the trains running, much less on any sort of a schedule. Each member of the group gets to go into the cab of an off-duty locomotive and see how complex it can be to operate an engine. (Joe called it a "railroad ballet.) "The "special" completes the circuit with another stop to explain and explore how and why the water is "deoxygenified" for use in the engine's boiler and how and where fuel is added.
The tour is about 50% about Disney and that may not be as interesting to your husband. I enjoyed most of it, especially the story of how they came to find the locomotives that are used, but was not as interested in some of the other information. It was all good but some parts were more interesting to me than others.
If your husband is a hard core steam RR buff, he will most likely find this informative. If he is generally interested, he will find it enjoyable. If he is merely interested, as my son was, it will be a 50-50 kind of activity. I'm glad that we did it as I put some of the information to good use later in the day as we rode it. I think my so would have rather slept in but went any way. You also need to note that the train is going to shut down around October for some heavy duty maintenance and upgrades. The shut down will last about 8 weeks.
To summarize, I really enjoyed it, my moderately interested adult son not as much but loves his dad and went any way.
Hope that this is of some help to you.