When I try to play a sound with the /playsound command, I hear the normal sound, and not the custom sound.
Steps to Reproduce:
1. Get a resourcepack that works in 1.6
2. Get a commandblock or just type the command, In this summary I'll use the sound "Chicken Hurt", so: /playsound mob.chicken.hurt johano1rct. You won't hear your custom sound, but just a chicken.
I can confirm that I am seeing the same issue - Windows 8 x64 bit (java build 1.7.0_25-b17) Minecraft 13w42b