I agree with that statement until the stupid bar on the right side is closed.
After that, it's a great GUI. Just don't try to use the WYSIWYG part or nothing will work properly in any browser except IE6...
I find TUI editing to be quite frustrating so vi, derivatives and similar make me crazy. Notepad++ for me.
Text editing is pretty simple at its core. You need to be able to:
Open or create a file
Move the cursor to different parts of the document
Type something in
Save a file
You access the new, open, save actions from a menu (or shortcut key). The keyboard and mouse allow you to move the cursor around, and the keyboard takes care of entering text in. Therefore most text editors only need simple GUIs.
A quick look at Textmate or MacVim won't tell you much about either. You may not even be able to tell them apart just by glancing at each for a few seconds.
Both are considered best of breed editors, yet look deceptively simple. Textmate IS simple to get into. Vim has a higher learning curve because of its modal nature.