This looks really interesting. The Amy Editor is an embedded text editor. This is not a WYSIWYG editor like the FCKEditor - it’s more like Textmate in your browser. It has a nice set of features:
- Syntax highlighting
- Smart indentation for each language
- Code folding
- Bookmarks
- Word completion
- Insert/Overwrite mode
- Unlimited undo/redo
- Intelligent character pairing
Not sure where I’d actually USE such a thing but it is an interesting concept. I could see Google buying them up and adding this to their online suite…
For heavy lifting it’s great to wheel out the IDE (CFEclipse, Dreamweaver, etc) but for those quick edits using an IDE can seem like overkill. A simple text editor is lightweight and designed for doing one thing well - editing text! 
A good text editor will offer syntax highlighting, code assist, search and replace, multi-document editing and more. Many support plugins or bundles to further extend their functionality. In this screenshot you can see one of the many text editing menus available in Notepad++.