FCKEditor 2.1 / 2.5 2.6.2 Recently I found myself looking for an editor for posts more powerfull then the standard built in editor that comes with WordPress. To that end I came up on FCKEditor (NOTE: No, it's not meant to be synonymous after the popular explative.) and so far it has been worth the install (See below for a screenshot of the editing tool bar). It means a bit less clicks on the 'Code' button for me, which I have been finding myself doing quite often with the built in editor. There are a few things I will miss with the old editor such as the ability to resize the main editing window an ability that FCKEditor doesn't seam to have (other then editing your FCKEditor options and manually specifying a predefined value.) I've yet to test many more features of this editor but so far many of my wishes I had with old editor have been satisfied.
All in all, and despite this one shortcoming that I find so far, I definitely recommend it to others.
Couple of issues encountered so far, however, despite them I still use the editor as it makes posting and creating neat and readable posts that much easier. However, here are a couple of things to watch out for.
Empty table td tags appear to cause FCKEditor 2.5.0 and WordPress 2.6.2 stall displaying content when editing the post again. Basically, the WordPress Editor and post content does not show up and some manual intervention will be required. Removing this tag resolved the issue in the case I've had, however you may have to do this through phpMyAdmin of your web host.
Another related issue is when deleting a table within the cell of another table. Doing so by right clicking and deleting the table appears to cause the same issue as above. To resolve this, I edit and remove the text manually from the source code of the post, which suggest there may be an issue in the source. Will have to look into this further later for more details.
In case you find yourself in this situation with WordPress, again you can use your hosts MySQL phpMyAdmin to edit the post text and remove the problematic tags. To identify them, I find HTML-Kit a handy tool for this purpose. In HTML-Kit use Tools – Check code using TIDY to check the syntax and identify any missing tags and other issues in the post.
UPDATE: Another attempt at resolving this seamed to work after removing empty tags such as the ones below
line 149 column 528 – Warning: trimming empty <strong>
line 150 column 823 – Warning: trimming empty <em>
It seamed to have resolved the issue in this case. Appears having too many empty tags can lead to the problem. Again, editing the code after getting the post content from within phpMyAdmin (above) can get you out of this mess. You can identify the errors with HTML Tidy. The UNIX / Linux command to clean up the post (after you save it in a .txt / .html file is to use this command from the prompt: tidy -ie mydocument.html. This will print all the errors that exist in your document and allow you to remove the problematic tags. The utility is from W3.org. These empty tags look to be the culprit behind these blank wordpress fckeditor editor windows.
Another time the blank wordpress fckeditor editor window went away when I deleted a number of autosave files from the actual DB using phpMyAdmin of my host. These are posts that have post_status set to inherit.
Another less subtle thing you may encounter over time is purely with usage. It get's addictive and going back to the original editor isn't really an option as the HTML tags the built in and FCK Editor use to structure your posts are different. You should definitely keep this in mind when using the editor.
UPDATE: Nov 29 2012
Fast forward to the future and we've updated to the ckeditor which according to reading is the closest one to the original, if not the original. In case you're interested, like I was, the source for the editor can be found at the development section of the site.
UPDATE: Jun 9 2013
With WordPress 3.5+ (though probably lower as well), you can remove the revisions for a post. Looks like queries and PHP has a timeout on runtime with certain hosting companies. Clearing the autosaves helps to eliminate this problem.
select * FROM wp_posts WHERE post_type like "%revision%" limit 0,5000
delete FROM wp_posts WHERE post_type like "%revision%"
to clear the autosaves.