On new sites I consistently don't notice any real dancing/sandbox effect when I don't use SB and don't get backlinks from heavily spammed pages. I just steadily increase my rankings (mostly on low-medium comp keywords) using tons of web 2.0 backlinks and nice content, and indexing my backlinks. But on all the sites I've used SB on, and either pounded tons of comments, or did manual high-PR comments, I went under a 1 to 4 week period of being in the dog house, then went on to gain meager rankings. So, some usefulness, but less. My case studies are only on 20 or so sites, so I wanted to see if anyone notices any correlation like this.