I've been a reader, moderator and meta-moderator since 1998 or 1997. Last fucking century.
I've read and participated in many of the flare-up (remember John Katz?) and redesigns. All of them have been an issue, but nothing like this one. This one really is different; it's not just old people bitching about "the new thing".
To be brief, the redesign sucks. It took a layout that is simple, clean, easy to read (and more importantly, easy to skim) and turned it into a "modern" mess. UI is hard. Really hard. This time, the UI team just missed the boat. The new design makes it harder to read the site. It looks prettier to some people, but it's harder to read.
Secondly, you shouldn't even consider changing over until the comments works. The comments should be the first thing you get right. When /. was born, there wasn't much else like it, but now there's a million tech blogs. What makes slashdot different is the comments. When the comments are broken, there's not much difference between you and Engadget.
Most of us only have so much time in the day to gather "news". I can scan Google news, Ars, Engadget, Gizmodo and all the rest, but when I want to read good commentary from smart people who have an interest, I come here. Kill that, and you're no longer the innovator you started out as; you're just another copycat.
Bite the bullet, admit defeat, and try again. This time, figure out why people like me have been coming to the same website for 15 years. Slashdot and Ars have been part of my daily reading, since I got on the internet. Two sites. Please don't make it one.