Given that and web design that sacrifices half the screen real estate for a sea of white is seriously broken, together with the fact that it's been that way since beta first came out in October, been complained about, and not fixed tells most people all they need to know about how much Slashdot cares about "user experience" and the feedback of the community.
I think that what Slashdot needs to do is simple: First, stop the beta NOW. It's sunk cost with a VERY bad outcome. Stop throwing good money after bad. Next, set up a discussion forum where users can give feedback on what they think is necessary - not on what you think is necessary. Focus the beta on that. Note that this is not to say that the designers at Dice should have no say - they should put forth their arguments as to how they think the site should change to attract new users (which is supposedly what they want and ALSO what we want, given that the community also wants a vibrant user base to interact with). After that, start making an updated site that is optional for users to use and, then, only after the initial usability gotchas are taken care of, start transferring folks over. Finally, always leave the old way for a backup for at least two major upgrades - I know that's old school and very non-Web gazillion.0, but it does help laggards transition.
If Slashdot had done this, I doubt there would have been this kerfuffle. And I know it would take longer and cost a bit more. However, if you actually believe in using feedback from your users when designing "user" experience (something that a lot of "user" experience designers don't seem to get), that's what you'll do. In any case, when what you're doing isn't working, you have to be an idiot to keep doing it. Alienating your current customer base is not a way to build an improved, vibrant site - Slashdot, you've had your Target moment. Right now you suck and we're going to boycott you next week to make sure you don't forget this. Show us how you're not going to suck in the future. That's really all you'e got left, unless you're going to start deleting accounts.