From what I have seen, there is a sandbox effect, but it mostly affects newly registered domains with poor quality inbound links that are focused on very competitive keyword phrases.
The easiest ways to avoid the issue are,
1) Use a mature domain that has been indexed for a while. This is one reason why so many site owners look for mature domains. I always set up new domains on a temporary site with a few articles related to the targeted theme. I do not expect the site to rank well for these articles, but the site does get indexed and the maturity clock starts ticking.
2) Good inbound links overcome almost every common problem with Google. If you can get a few links from authority sites that covers a similar topic, you probably will never see a sandbox effect. That is probably why a lot of you have never seen this. Will, you have several large authority sites, so I would not expect you to have a problem.
"Democracy is two wolves and a lamb voting on what to have for lunch. Liberty is a well-armed lamb contesting the vote." -- Benjamin Franklin