I'm a SEO guy, I can't say I'm an expert SEO but let's say I'm semi-professional SEO guy with some experiences...
I noticed a new thing Google is setting up since the Panda 4.0,
Google won't let new websites rank easily in the first pages (even if the website is unique and the keyword you are targeting is extremely LOW competition).
Since Panda 4.0, one of my websites got hurt by this update, I moved on, and created a new website targeting a low competition keyword.
With my experience, after a good on-page optimization it takes Google average of 2 Weeks to rank your website no less than PAGE 3 (I'm talking about a low competition keyword). Then after some unique content publishing and steady writing, the website could jump in first positions in 1-2 months average.
Now, after Panda 4.0, I noticed a new Sandbox being applied by Google on new websites. My new website can't pass the 5th page (and not for my primary keyword target), and even no rankings for other keywords...
The question is: Is this new Sandbox going to last so long?
I saw this problem with a lot of SEO experts published on forums, they are always predicting it will last a month and then it goes off...
I hope this Sandbox will get down by Google... because it's a very hard hit for SEO and new websites, we can say: No More Google Opportunities !