I did have a Xarthisius, Gaunter, Guardian deck (plus other cards that see opponent's deck), but i deleted it this patch after 5 losses in a row. Maybe it was bad luck and not the deck's quality, but i wanted to try new decks anyway.
Also, careful with Reinforcement (NR silver), Nature's Gift (SC) and Marching Orders. I've been screwed by those cards, putting dangerous golds and silvers on the bottom of their deck, only for them to be summoned with those cards anyway...
I think it's main purpose is to see your opponents deck so you can set your game up accordingly.
Nice to use in R1 opening and R2 when your opponent drypasses but totally useless against mulligan, spelleithne, mill, many NR setups and basically any deck that runs Royal Decree. Only useful way is to send an effective silver (like Morvudd) to the bottom (or hope your opponent has all their golds in deck so you can put a critical one like royal decree/geels/renew to the bottom)