Depends on which section you read. I introduced my fiancee to /r/IAmA and she thinks reddit is mostly about child molesting drug-dealers who fly fighter-jets and rescue endangered species, because they were raised in a polygamist cult family living in the Everest base camp.
To me it's mostly proggit, hastily scanned once every 1-2 days.
/. has had editing problems, but the comment quality has not, to my experience, dipped that low. It's not as high as HN, but it hasn't dipped that low, either.
HN and /. are on opposite ends of a spectrum--HN is what happens before the trolls arrive, given you seed the community well, and /. is what happens after the trolls leave.
I always though the biggest problem with slashdot was that the moderation somehow lead to an extremely insular community. There was a prevailing "slashdot" opinion and that was pretty much the only opinion expressed in highly moderated comments. I was a reader for years and that's pretty much why I left.
What's strange is that slashdot moderation isn't that different from any other site, but for whatever reason, I think it hurt slashdot far more than any other site. Maybe, it's just that by default not that many comments are displayed as opposed to reddit or hn, so it's all the more noticeable when the top 20 or so comments all are basically the same.
I usually found a lot of highly moderated comments opposing the "Slashdot groupthink", particularly ones that criticized the "Slashdot groupthink" by name. But there were a lot of shared cultural assumptions there as well.
Or maybe I am wrong, Slashdot has been starring their paid subscribes for ages, but I am not sure reddit wants to stoop to slashdot levels.