If it s nofollow it still gets indexed by gooble, just no pagerank. And yes Digg it is great if your site should get indexed fast.
Digg is great site..You can get backlinks.. I prefer to use Mixx,if your site will be indexed by Google. Relatively Mixx is better.
I've had a great experience with linking dfeom digg. Many page hits in a short period of time and quick google indexing. Definitely recommend this.
I imagine Digg links can bring fair amounts of traffic if you get plenty of diggs. However, the system is a little too corrupt for me with friends digging each others material. I therefore don't bother with it.