My tax return was accepted on January 27th, but my refund is still not approved, Why?

I submitted my tax return with TurboTax on January 27th.  The smart check said that there were NO ERRORS.  The IRS accepted my refund within hours of submission.  However, her I am more than a week later and when I check "Where's My Refund", it is still not approved.

 

Meanwhile, several people I know filed days later than I did and their refunds are already approved and a payout date provided.

 

Why is this and should I be worried?