IF you're doing a block exchange, it's important to use 1/4" seams, for the pattern given.
However, if you are not exchanging a particular size block . . . .
As long as your seams are consistently the same width, your blocks will turn out fine. Even if you use 1/2" seams, your blocks will be fine and your points will match. Downside is the blocks will be smaller and you'll need more fabric to make extra blocks, for a certain sized quilt. OR you can start out with the cut pieces larger, to accommodate your wider seams (you'll still need extra fabric, for these wider seams). Consistency is what's important!
When I make quilt blocks for dog beds, I always use 1/2" seams. My points match and unless you look at the wrong side of the block, you'd never know I used wider seams.
Bottom line, find "your" perfect seam width and go with it. Use the side of your presser foot for a guide, if it's convenient. Use a line on your machine. Use whatever works for you and concentrate on consistency, rather than that perfect 1/4". BTW, Inever use a slight 1/4", unless it's by accident!
Meant to add - in addition to the thread used, the thickness of your fabric also influences your finished block, once the seams are pressed. If your seams are accurate but your blocks are still a bit wonky, make sure all of your fabrics are of the same thickness/weight.
Last edited by Neesie; 09-15-2013 at 05:40 AM.