== is not slow when types of operands (in typeof sense) match -- then it's equivalent to ===.
You'll find a lot of == out there, or would if only Google code search were still up.
Hey, I got to answer with the one thing I'd change. There are more than a few, and I had to pick. Losing the equivalence relation I had in the first ten days (apart from NaN != NaN of course) was my pick.