while i mostly agree, it does make it clearer that it's your progress across an entire article: with just the scrollbar you never know if you'll be facing "page 2, 3" links at the bottom.
I often wonder how far an article really goes. A lot of the times there are tons of content below the article, or perhaps just a long commenting thread twice as long as the article itself (or, as stated, a multiple page article (which you don't know about in advance)). I often scroll down for the sole purpose of finding out how long the article is.
I really like the information the New Republic conveys (but I dislike having a bar on top like that).
What is it with these sites that break down articles into several pages? NYTimes is a particular culprit that annoys me. Does anyone find an article easier to read in this format? I presume it is to force more Ad views on people?