Traffic and backlinks. Traffic will likely just be a trickle but if even one visitor converts you are ahead of the game.
In addition to the links directly from the bookmarking sites, visitors who like your site may link to your site from theirs. Another big plus.
is it something that should be used instead of a RSS feed or pinging a site?
It should be done in addition to your RSS feed and pinging.
It may be good, but I've never heard of wirefan. I just stick to a couple of big ones and do get the benefits I listed. The two I hit are:
It would also be a good idea to look for topic-specific bookmarking sites. For example, BizSugar
focuses on business blog posts.
You can find more here:
50 Social News Sites
Again, the results I get are not earth shattering but it takes very little time and the long term benefits are worth the effort in my opinion.