If u have really Unique and Great Content then yes it can just need 50 + Diggs to reach on the home page of Digg and you might get huge traffic
i got thousands of hits from stumble upon, so it is hugely possible that digg also sends traffic! i have never used digg for making traffic! but then first check out that your host can take that much traffic! am sure you don't want to see you site out of bandwidth!
Digg can give a massive bump to the traffic. If you reach the front page of digg, consider your server blasted. But the traffic from digg is not worthy. It never converts well.
It doesn't convert well, but think of all the backlinks you will get from it. I definitely think it's worth it, but if your website has Adsense or something like that then maybe it's a good idea to take the ads off for a short period. In my opinion it's worth it though, no doubt about it.