I like following things Content Management Systems (CMS) Blog platforms Email editors Documentation systems Any web application requiring rich text input

We used CKeditor as part of the development of an internal media workflow. The integrated features of CKeditor allowed us to enhance collaboration between users through the comments plugin, and also enabled us to integrate our own designs into the interface. We also developed custom plugins to meet our specific needs, and integrated a library to add documents linked to the HTML document. We are satisfied with the product.

To use CK Editor as a formatable textarea, there is not much to do. It can easy be configured and support various of formatting options out of the box. What helped us is, that it is expandable. If there isn't a feature, which CKEditor provides out-of-the-box (or buy their paid services), you can write your own plugins. Once you understood their events and what they provide, it is highly customizable. And if you can't figure out an issue yourself, the customer support has an open ear for you everytime. Since we are a paying customer, i can't tell anything about the customer support, if you use the free version. The documentation has many examples and showcases, so it sould be easy for you to integrate it into your app. Since we did our own plugins, we compile as well our own CK Editor on top of the standard one. It took a bit to understand, how we should do it, but an example project helped us with the start.