Having tried all the free WYSIWYG editors available, JCE seems to be the most complete one. It does a good job. BUT still A FEW IMPERFECTIONS REMAIN.
Most annoying is the embed media functionality that... simply doesn't work. Not only it doesn't work, but if you want to embed a video typing the HTML code manually, JCE will just strip out your custom code! I had to revert to the non wysiwyg editor to embed the videos in my content!
Neither you can create pop-up window links as some other free editors do.
The image browser is good, but it doesn't let you browse the whole site. You're limited to the Joomla image/stories folder. It would be better to have access to the whole site structure, at least if you are administrator or super administrator.
Despite these few negative points, JCE work well. Apart the embed video problem, I haven't noticed any other major bug. It's also quite fast and efficient.
If you mostly use text + images content on your site, JCE will do the job nicely. If you have more complex content, or want to add some custom code and JCE doesn't like it, you may become frustrated.
Owner's reply:
JCE has a Media Manager plugin that helps with inserting media.
Following the release of 1.1.0 'stable', the Media Manager SE will be available, with the ability to insert FLV files.