I'm also rather disappointed to see the stereotype "we hate everything" characterisation of Slashdot from a couple of posters here. That's like saying HN is just full of college kids who think making a social web app with geolocation and a REST API is going to turn them into gazillionaires when they pivot to something useful (after all, the idea doesn't matter, it's the people who count) and then get acquired by Facebook for the GDP of a small country.
Obviously there really are quite a few young, delusional people on HN, but I don't think most of us spend time here because of those people. Obviously there really are quite a few very negative/selfish people on Slashdot, but I don't think most of us who spend time there do it because of those people, either.
Incidentally, as I write this, Slashdot's home page is full of topics that might have been (and in several cases have been) popular on HN as well: several articles on new technologies, several popular science articles, commentary on issues like piracy and privacy, and so on. There are some decent comments in the related discussions, too.
That all said, I don't go to Slashdot as much as I used to. Partly that's because they keep messing around with (and often breaking) the basic design and functionality of the site. Partly it's because a lot of the stories are old news by the time they get past the editors, and they've already hit the front pages of HN, relevant subreddits, etc. Partly it's because the discussions are too big for a simple chronological ordering to really work and the system for filtering by moderation score doesn't seem to help much. All of these things make the site more frustrating than it used to be, and I suspect if Slashdot is indeed on the way out there will be plenty of places to point fingers.
But please can we not descend to the level of "Oh, those people on {other site} are just {arbitrary negative stereotype}". Such generalisations can be levelled at any popular forum site on the Web, and they're about as useful in each case.