I've never bought a kit - I agree with Clover Patch. First, I may not like all the fabrics. Second, I know me well enough to know that if it needs 1/2 yd, *I* need 3/4 :)
I have however had a pattern with a mistake. My first quilt too and I'm so proud that I recognized the error and was able to compensate for it! The pattern was "Bento Box".