Chris Latham from Engineaudio has published a video with his top 10 changes to the Unreal Audio System from UT3 to UDK.
10. New Sound Actor Icons
9. Multiple Sound Slots for AmbientSounds
8. SoundGroups are now called SoundClasses
7. SoundClass Editor
6. Ambient Zones
5. Visual of Min Radius
4. Switch from OpenAL to XAudio2
3. Improved Distance Models
2. Improved Low Pass Filters
1. Content Browser
Did you like UDK? What are your favorite tools there?