Right after the anticipated Q2 SP1 is out, let me introduce some of the features that make Telerik RadRichTextBox proudly prefixed by rad and rich.
Since a picture is worth a thousand words here are some six thousand words for you :)
Zoom in/out:

Click here for online demo.
Integration with RadBook:
Click here for online demo.
Actually the new documents presentation controls allow even scenarios such as this one:
…but we will need your help with more real-world stories about this one.
New properties- "Xaml", "Html", "Text" allow binding in Xaml, enabling MVVM scenarios, easier usage with databases, RIA services, DataForms...