Different Search Engines follow their own approach on how to assign value to a backlink. The values could be based on the quality of the backlink website as well as the competition. As soon as Google Bots detects & assign values to your backlink, you can see the changes in the SERPs results. Older backlinks do carry a more weight than the new ones. To find out of a link is counted, the first place to check is the Google-cache. Its known that good, quality links can affects the SERPs within 48 hours. It clearly indicates how fast your backlinks can take into effect. Backlinks plays an important role for higher search engine rankings.
Backlinks from High PR pages carry a lot more weight than the pages with lower values.
Also, link:www.domainname.com tool from Google is not fully reliable. Do check with external link popularity services such as: http://www.iwebtool.com/backlink_checker.
