Two of the biggest features are the addition of indentation based collapsable code regions (I've already got collapse/expand hotkeyed!) and "Copy as HTML" which allows you to copy the contents of the workspace as HTML which retains the formatting and your environment colors! Awesome! This makes it perfect for writing up web based documentation.
Aside from this, 2.3 also introduces other features like the new "Find in Directory" command you can use on the directory toolbar, the "View in Browser 2" command which allows you to hook up IE and FireFox (or IE6 and IE7) to have seamless browsing with one and external launch with the other, and various bug fixes with the FTP component.
All in all, an awesome version that has some loooong overdue features. If you don't have it already, nows the time to download it!