I have been visiting this site for many years, and find the current version 2.0 decent (after a bumpy start). Slashdot has stayed mostly interesting while the user comments are sometimes funny and useful, insightful, etc. I have learned a lot from this site so I have a strong desire to see it stay healthy.
However, you risk losing exactly the types of users who make the site worth visiting. How would this new design appeal to a technical person who wants to quickly scan through to find a few stories or comments to contribute to? The answer from the above comments seems to be that these types of users won't bother fighting against this terrible design and will leave instead.
Biggest problem with the Beta: The new design forces too much scrolling which is a nightmare on a site where the the pages are long threads. It flies in the face of common sense. Even the BETA Classic View is clumsy and awkward to use with wasted space everywhere. Perhaps if you make the classic view much more compact - like the current version of the site - then you might keep a portion of the loyal users.
In short, if the new design is adopted without significant improvements, I will probably stop visiting Slashdot. And I fear many others will as well, and that would be a sad ending for a once great forum. Please don't ruin Slashdot!