Never really took notice of Chaos Wand properly before. I have had it played against me, I think it did some work.
The Paradox Engine combo is pretty nice, from artifacts and you should be able to cast all the instants and sorcery in opponents decks, however you are likely to hit a number of board wipes. It is a "may", so you just need to make sure you have a backup spell yourself to keep the engine going.
Also runs into the problem of hitting a counterspell effect which if nothing is on the stack, then you won;t be able to cast it.
I guess the trick is to keep using it when you get to untap and the spells are still on the stack, just to make sure there are more options available for certain cards. Things like copying spells, etc.
I think I'd prefer it in a deck that has some ability to search through your opponents library to scope out what is going on. Things like Thada Adel, Acquisitor, Rootwater Thief, Sphinx Ambassador, Bribery, Acquire, Knowledge Exploitation.