Some people say it's great and some consider it spam. Is Digging each Article and Review on my site spamming? is it worth it? http://hardwareinsights.com/
How long are the people staying on the page and do they look at other pages on your site. That will be a better indicator if it's worth it. Second to actual sales that is.
It's totally fine, but I suggest you limit your Digg submissions/bookmarks. You can get banned from Digg. The site is so strict these days and only accepts quality backlinks.
If you do this for a couple of weeks or more then digg may be restrict you from continous bookmarking. Also they are very much strict in this category. So be in patient.