There are some weaknesses, sure. Asimov himself was even aware of some of his weaknesses as a writer and talked about them occasionally in his memoirs and such. But, aside from HHGTTG and Dune, I can't think of anything that I've re-read more often, or that has been a more satisfying part of my reading life (and I read a lot). Asimov remains my favorite author after all these years. Admittedly, some of that is the "old friend" factor. But, nonetheless, I believe it is very solid sci-fi, and recommend it to anyone who hasn't read it.
I thought the original trilogy (Foundation, Foundation and Empire, Second Foundation) was amazing.
I also thought Asimov really, really, really should have stopped there.
I don't know what changed - it's a shame, since I was really looking forward to it. It's possible I'll give it another shot in a few years.
To clarify: I'm not saying that people should shoehorn women into stories to satisfy a quota, I'm saying that stories that include women are simply more interesting, because they display a wider range of humanity and of the human experience.
Or, to put it another way, it's just boring to read a story where all the characters fit within a very narrow range of personality.