The introvert/extrovert dimension is as predictive as the identical dimension in the Big 5. I've made great use of knowing when a colleague, friend, etc. is introvert or extrovert regardless of which test told used. Even if MBTI didn't quite hit the mark historically, I don't see why there are so many haters. It's part of working towards better models. It's a worthwhile pursuit to try to characterize stuff like personality. MBTI is strictly more useful than Astrology just as BIg5 is strictly more useful than MBTI. Future models will surpass these with things like hybrid self-report + neuro-imaging approaches. People really seem to feel threatened by being characterized though. It's a bummer.

I certainly feel threatened. If you knew about my "pre existing condition," you'd know that I'm threatened by information that claims to be an authoritative record about me, that I can't control, and whose use I can't control.

I can't prevent any "unofficial" interpretation of this information.

Making it "better" only makes it more threatening, by making it more believable or making it harder for an intelligent person to game the test.

Myers-Briggs traits are correlated with big five, so if you believe one has predictive power then so does the other.