Tom's Hardware Guide published a review on HP Z27q 27-inch 5K Professional Monitor
A quote from the article:
Just as we're getting acquainted with Ultra HD, HP has upped the ante with a 5K monitor. At 5120x2880 the Z27q puts a whole lotta pixels on the screen, 14,745,600 in fact. Today we check it out in our lab.HP Z27q 27-inch 5K Professional Monitor Review @ Toms Hardware