I've made two of those. They are very cool looking bows. I think the main advantage is that you can make a shorter but more powerful bow, compared to a single bow. The draw force curve is not much different, and they shoot pretty much the same as any other wooden bow. The geometry might be optimalized to give a somewhat fatter draw force curve, but I would not expect anything significant.
However, I'd say go for it. They are not so difficult to make either. There are old original examples of the type where the small bow has no reflex, but that would really not bring much of performance to it, so I would suggest to heat at least a couple inches reflex into the small bow. I used steam first and then heat treated the small bow to give it 4-5 inches reflex. Another issue with these bows is that the main bow should be pre-tillered with slightly more bend in the middle, because once the small bow is attached it will force the bend closer to the tips. Nothing major, though.