Digg is working, but the problem is it has a limited features. They only have a maxium of 100+ words for their content, that is why you cannot include your whole content. Plus the image is also limited. But Digg is sure a good source of traffic and a good backlinks.
Last time I checked I still had a backlink from digg to my site. I think it is still a good place to go for webmasters.
Digg's comment link is dofollow. If a digg's site got PR juice, try to do some comment and insert your link. This will be a dofollow link.
Digg does tend to help your posts get indexed fairly quickly and their pages does rank at times pretty well in serps, always helping you get those extra visitors. I am not sure about its position to pass PR juices...but I don't care for it! Regards, RightMan
Logged in users will get directed to a shortened URL But anyone who isn't logged in (including search bots) will see a good old-fashioned do-follow hyperlink. As far as I can tell, it still passes juice along to the original source.
As far as DoFollow - Dig doesn't do that. Also Stumbleupon. Great way to get traffic - but for good 'ole SEO backlinks - forget it.