You need to be rather careful when using this trap.
The requirement is that you must select 2 set spell/trap cards. It doesn't specify only your opponent's.
So what can happen (if you're not careful) is that if you activate it when your opponent only sets 1, this trap card will force you to select one of your own set spell/trap, effectively locking yourself down as well. Locking down 2 of your opponent's set spell/trap can be rather tricky if your opponent uses them often, before you can wait for them to set 2.
Totally agree. AMAZING card to play when the duel is lagging in such a way that you know the opponent has Mirror Wall (or less commonly Order to Charge/Windstorm of Etaqua) set. Also great in a pinch when going second and the opponent laid down a bunch of set cards.
Goodness this card is crazy. Blocks 2 of 3 of the trap zone. Only way to get rid of it is to remove trap SPELL card. What the...