(For a video demonstrating these changes, see this page on the Video2Brain website.)
A lot of the changes that we made for Adobe Premiere Pro CS5.5 were to remove inconveniences, sources of confusion, and clutter. One small but very welcome change is the unification of the audio effects.
Previously, each audio effect had three instances—one each for mono, stereo, and 5.1 audio tracks. This was a nuisance.
In Adobe Premiere Pro CS5.5, each audio effects just has one instance. This makes applying the effects simpler, and it cleans up the structure of the Audio Effects folder. When you apply an audio effect, Adobe Premiere Pro automatically applies the effect of the correct type, corresponding to the item that you applied it to.
Some effects have restrictions, and can be used only on certain track types. See “Audio effects” for details.
For a complete list of what’s new and changed in Adobe Premiere Pro CS5.5, see this page.