Well, it is quite plain and simple, but has brick build parts, and still, an affordable castle.
I see this as a "starter" to the modular system, since it could be expanded further with the whole series of little buildings (you know, from 6040 to 6067...).
So it is good for those reasons but can be decent as a stand-alone too because it has a consequent play value/size-price rate. Perhaps it should have integrated two generic soldiers with round shield to be able, if needed, to part opponents off the set itself.