I have the WYSIWYG editor working for Wiki pages. Did you try looking under Admin->WYSIWYG (It has its own admin page besides the Features)? There is an option there that says "Reopen with the same editor", although I have no idea what this means exactly. Mine is checked, which I assume must be the default option.
As far as experimental goes, I've noticed some quirks like it suffers from a similar "extra line spacing" problem that Microsoft Word also has when dealing with HTML text (I guess this is more to do with HTML itself). Another quirk is that existing Wiki markup doesn't always seem to get processed nicely and will display as one huge long line. However, all that aside it works reasonably well and would be good for users who are not as comfortable with computers as others.
I personally will stick with marking up text by hand, with the occasional use of QuickTags, but the WYSIWYG does indeed work.