From now on, page rank will be as good as shared, when you link to a page, with no exceptions. Link to a page and use nofollow on it will waste the page rank that you did not want that page to get. It’s like the blocked pages will have their share of the authority but, they will not get any because of the nofollow on them. The total authority will always be divided upon the total number of pages you link to – blocked with a nofollow or not. Imagine you have a toggle switch to turn nofollow On and Off on a number of pages but when you operate the switch now nothing happens anymore.
However, as Danny Sullivan and those (people I admire) who’ve left comments mentioned, reasons why we do sculpting vary.
Anyway, I believe that using nofollow definitely will increase rankings for pages. Because it would be clear to the search engines which pages we want their crawlers to focus on more – i.e. landing pages. Even though I wasn’t using nofollow before for page rank reasons, I was using it for the practical reason that I was selecting which pages I really want to appear on the SERPs. You come to think the same way only if you stick with the basics first and then applying your sweet ideas on top of those. So when changes like this one arrives you won’t have to do anything but read about it.
For example: Upon using PHP, I didn’t use nofollow on login page, register page, etc., BUT, what’s on those pages and the pages where the user will be re-entering to go back to where s/he was after logging in, are written or will yet to be written by external PHP scripts automatically. I was surprised why they are making such a big deal out of the latest change by Google when I’m sure their websites use far more advanced technologies than mine, although I can safely say that my techniques materialized by always thinking of ways to stay in the “white hat” category. That’s my way of thinking ahead to make sure however the rules change, the site will not violate any search engine guidelines – including Google’s.