I know it has problems - but most other WYSIWYG editors have exactly the same problems.
As some of you know, I've got an add-on which allows you to create notifications.
I decided that, rather than a plain textarea, I would have a rich text area that accepted HTML code. So I tried several editors. CKEditor, SCEditor, CLEditor, Redactor, jWYSIWYG... none of them are very good at all - at least no worse than TinyMCE.
In the end, I've decided to implement TinyMCE in my add-on. I'm achieving this by using the version of TinyMCE included with XenForo, but calling it with a completely different set of options and without the XenForo specific plugins. I now have a familiar looking editor (with some options removed) that accepts HTML.
I know it's not perfect, but anything that is a good and functional replacement has to be something special.