Heh! The pad speaker is a brilliant little feature of the DS4, I'm really enjoying listening to the audio logs scattered throughout Vekta in Killzone through it [I like the volume quite high myself ]. I'd imagine that would've worked well for something similar last-gen like, for example, the audio logs in Bioshock. I can see that the DS4 speaker would also be good for freaking people out in horror games too; hopefully Shinji Mikami utilizes it in some way for The Evil Within!
Ha, this is exactly what happened to me. I didn't know the PS4 even had this feature, so when I played Resogun I near threw the demon controller across the room.
Useful tip. Turn down the audio level on the DS4 pad. It comes set at 'Shit-Your-Pants-First-Time-You-Hear-It' and needs to be lowered to 'Oh-That's-Better'