I think quality and relevancy of backlinks is important. Domain extension do not count when talking about backlinks, except for sites that is optimized for specific geographical location.
I saw some positive change when I had a link from a .edu page. Although I had other links from regular .com's with higher PRs, this link pushed the site up.
*.edu links are certainly important in determining your serp. well I did some experiment on this, take a look at this site -> www.duitsaku.com it doesn't have many backlink from other sites, but with links from *.edu.my and *.gov.my, they are certainly on top 3 for the keyword "duit"