Is this obvious?

wow, 3 sec to understand what mates!

With tactics trainer, I find that sometimes if I go after too many puzzles in one session I end up missing 'easy' solutions like this. Often because the puzzle looks like another with a slightly different solution and I start moving a piece only to realise that there is a mate in 2 or that I'm currently in check or some other silly thing.
I imagine alot of people do things like that or think a puzzle is more complicated than it is and take too long to solve things.
I find stopping myself from making assumptions like this has actually been the best lesson I've received from tactics trainer.

wow, 3 sec to understand what mates!
3 seconds to recognise a fool.
Ok, warn me. meh...


I'm also in the 12-15 range which is unusual for me for a mate-in-one. I began looking for ways to win the queen before I said, doh, there's mate! Given the responses in this thread (>10s), the difficulty level assigned to it is reasonable.
Find the best move as quickly as you can without making an incorrect move.
This puzzle is currently rated 1789 on Chess Tactics Server. That means that people rated a bit lower than that usually fail to solve this puzzle or solve it in over 10 seconds. Did you have any trouble with this?