Back in the day when I first started quilting and Simply Quilts with Alex Anderson was on TV (which is where most of my quilting education comes from), she had a guest quilter on one of the programs and the subject of seam allowances was discussed. The very renowned (sorry, don't remember who) quilter's advice was to certainly strive for a perfect seam allowance but more importantly - be consistent! As one of the other poster's here said, all things being equal, if my quilt is a half inch smaller than the pattern calls for, I'm good with that as long as my blocks line up properly (with or without a bit of fudging along the way).