WordPressI just had quite some experience using WordPress 2.x's new WYSIWYG editor based on Tiny MCE, while publishing documentation for 3 column Anaconda Theme for WordPress. Two word summary of WYSIWYG editor: it sucks.

This new WYSIWYG is frustrating to use at every step of the way. It is buggy like the worst Microsoft products. The WYSIWYG mode isn't properly synchronized with the HTML mode. Any changes made in the HTML mode may or may not get into the WYSIWYG mode. Often a change made in HTML mode isn't idempotent. In other words if you make some change in HTML mode, then close the window and then go back to HTML mode, some of your change may be lost or worse modified.
Button implementations are buggy and insufficient. For example I cannot create a anchor tag with name or even a page (you can use my multi-page plugin for that). I needed to create anchor tags with name so I can redirect people from content section to other sections of the site in the same page. I switched to HTML code and created the code. When I switched back there were three tags created for each insertion. And worse it isn't consistent. So for some it came out fine and others there were 2 duplicates.

It inserts innecessary tags and invalid tags and often stubbornly refuses to correct despite persistent efforts. For example my last section was coming out in all bold for some strange reason. In html mode I found that it created a strong tag without a corresponding end tag. I removed it and saved. The display way still the same and wrong. Repeated efforts to correct it were unsuccessful. In the end I switched over to non-GUI mode and hand corrected all the code.

I think the WordPress WYSIWYG mode is so buggy that it should be simply dropped. And definitely it shouldn't be the default. It is bound to give a bad reputation to an otherwise reliable software.