Been wondering about this, now that Safari on Mavericks comes with the Power Saver "option" that replaces flash videos until you click on it, is ClickToFlash/ClickToPlugin useful anymore? What do they do that the new Safari Power Saver doesn't?
Absolutely still useful.
Not only can I view YouTube in H.264, it gives me options to download.
Also, set preload (or not), autoplay (or not), preset volume level for the media player, and control lists for which sites can use plugins without having to click (whitelists and blacklists). There are more, but those are just some features I use in ClickToPlugin.