On the one hand, putting this into the deck means that you have to pay 3 mana for your Secret. On the other hand, you get much more flexibility. Depending on the matchup, board state etc. you can just pick the best Secret possible. For example, people have been putting Rat Trap into some builds a while ago and it was very mediocre. It was amazing in some matchups, but in others it nearly never (or really NEVER) triggered. To be honest, I would gladly put this instead of Rat Trap in that deck – I could still pick Rat Trap in the matchups where it matters, and I could have an extra Explosive Trap against Aggro etc.
If you play a Hunter deck with Secrets (like Spell Hunter) + Lesser Emerald Spellstone package, you will probably want to take out the more situational Secrets and replace them with this. Paying 1 extra so you can make a choice each game is worth it.
Heck, you might even want to play it in Prince Keleseth version of Recruit Hunter just to have access to Secrets. It might fix some of the deck’s weaknesses, like lack of AoE.