The sandbox effect doesnt even exhist to me, high ranked keywords have alot of backlinks, if you have alot of backlinks you can instantly compete with them. That is where i think people mistake the sandbox with something else. This rumor is like the people saying that .gov and .edu links mean something more. I actually agree with matt cutts on this one and i have already thought of this before. He said they dont mean anything else. Now lets break it down.... Alot of people link to .gov sites and .edu sites. This is why they are so special to get a link back from. not because they are a .edu or .gov Sandbox doesnt exhist in my eyes read what you were saying, "competitive or even a semi competitive keyword word " if you have the links like those people it wont be a problem.