Here is the list of new features and improvements from the release notes:
New Features

Support for metadata.
Added a signal generator.
A configurable special pasting that automatically fades in/out.
Added an icon for the files saved by TwistedWave.
Added the ability to export the selection.
Added the ability to create a new document with the current selection.
Added […]

From the release notes:
New Features

Added the ability to move the cursor to the next transient.
Saving OGG/Vorbis files (only reading was available).
Reading WMA files.
Added the ability to disable the automatic scrolling when playing.
Added the insert silence effect.

Fixes and Improvements

Improved the audio units management.
When loading a split multichannel file, the document name was Untitled.
The audio […]

Along with the ‘New’, ‘Open’, ‘Save’ and other commands you usually find in the ‘File’ menu, you may not have noticed the ‘Duplicate Document’ item. How useful could that be? Don’t you get a duplicate document just by saving it with another name?
Working on an audio document often involves many steps, copy/pasting, applying several effects… […]

From the release notes:
New Features

Ready for Leopard!
Reading/Writing FLAC files.
Reading OGG/Vorbis files.
Saving CAF files.
It is possible to choose the sample size, bit rate and codec when saving a file.
Added the cursor position and (optional) selection length in the toolbar.
Added two dialogs for editing the cursor position and selection.
Added the ability to reorder the channels.
The file […]

Editing a sound file consists mainly in copy/pasting and applying effects. Although TwistedWave lets you copy and paste bits of the sound file around in no time, applying a sound effect affects every sample, and takes more and more time as the file gets longer.
Repeatedly applying effects on a long file becomes a very tedious […]