Although I have tried a quasi form of this, I cannot say that I gave it a fair shot.  So I cannot give a real good opinion either for nor against it.   I can say that they are not a set it and forget it solution.  They have just about as many needs as your main tank.  Dumping in X inches of sand then building your aquascape on top of it is much less than the ideal way to set one up.  If you would like to read about the main benefits as well as the potential drawbacks I would suggest looking that information up on the web.  Many a hot debate has raged over at Reef Central, maybe peeking into some of them will answer any questions you have.

    Be prepared to take in all the details of both sides of the debate before either going with it or choosing not to.  For what it's worth I think the idea of using more than one of them set in series and remote to the main tank is about the smartest way to use them.  That would make swapping them out when they are loaded up a rather trivial thing to do.  Having more than one allows swapping without loosing the entire area of the DSB.