My experience was that I had already thought about many things that Eliezer described in the Sequences, except that he took the thought a bit further, and then connected it with some other thoughts. Also it felt awesome to have a social proof that I was not the only person in the world thinking about “weird” things.
I assume if one never thought much in that direction, then the Sequences would simply be too much, too weird.
Most of the ideas in the Sequences are available elsewhere, too. You could probably get 90% of the information by reading five carefully selected books. I still appreciate having them neatly collected, and connected in what feels like a coherent whole.
Maybe just as important are the things that are not in the Sequences. There are many books out there that mix good stuff with bad stuff. I like the absence of applause lights, mysterious explanations, arguments by definition, etc. There are many smart books and smart people, who just can’t resist doing also something incredibly insane (by our standards). I already had a bad feeling about that, but couldn’t articulate it.