sneak peek accuracy

Has anyone taken the sneak peek sex reveal test and had the results be wrong? I ordered it all excited and am very, very good at spotting scams so if this is one, their marketing is brilliant. I am just worried I may have wasted money but the website is SO convinving, and the money back guarantee, but it's a little odd that it's only after the baby is born and not after sex is revealed in an ultrasound.