Well, I was about to start work on new Parser / BBCode Manager, but what stopped me is editor integration. You see, if new bbcodes are added on the fly, you have to provide not just patterns for them, but also tips (with all the translations), icons, etc. And you can't do it editor-independent. Supporting multiple editors will be a hard pain, whereas there is no ultimate editor available.
I like Textboxer because it's lightweight and yet functional, so I could even deal with AJAX preview instead of WYSIWYG, but when it comes to extending it on the fly, Textboxer sucks. Most other bbcode editors don't have WYSIWYG option, which is most requested nowadays. Most WYSIWYG editors don't have bbcode support (or have ugly inconsistent bbcode support). So I'm puzzled since I really don't have time supporting even 2 editors instead of 1.
I even think of moving off from bbcodes to html completely (providing migration tools and backing up security some way).
May the Source be with you!