Did you even try the site?
Even my Palm in 480x320 portrait mode displays slashdot.org much better than the N800 in _any_ mode. Whatever you do in the N800's landscape mode you can't get that site to show more than a small amount of information at the time.In portrait mode you'll simply adjust it sideways until you have the articles screen filling the whole screen (with or without zoom as you prefer), then page down with the D-pad (if you have that one properly configured). Much much better than what's now possible.
Ah, and I don't understand what you mean by 'the cost of column width'. The whole point is that with portrait mode you adjust the N800 to the site's enforced column width. As a reader I don't care about the _other_ columns - all the information is in the central column.