My quilt guild did a 'block of the month' and we all made blocks and a winner was picked at the end of the month. That is when I learned that a 1/4" seam is not the same in everyone's mind. Even cutting out squares of the same size isn't the same. I always thought, for example, that a 6" is square is 6 inches on all sides. Not so, for everyone. You might get 6 inch square that is only 5 3/4" on one side and 6" on the other 3 sides.
I learned the best way to sew with others is if you are doing a community quilt, for instance, that you use a very forgiving pattern where you don't have to have exact measurements. Otherwise, if you are doing a quilt for yourself you do all the quilting for yourself and even if your square isn't a square or your 1/4" seam isn't a true quarter inch, at least you will keep it consistant and most likely your quilt will come out okay. Mixing different sizes from other people's work just doesn't mix.
A recent experience of mine happened at a quilting retreat I just came back from. I was tired and didn't want to sew anymore (it was 9pm and I had been sewing all day) so I decided to help a friend take the papers off of her foundation blocks. The block was very simple, just strips that went diagonal on a 10" block. This lady is a prolific quilter and is always turning out a different quilt each month. With all of her experience quilting, I expected that she would have perfect scant 1/4" seams. Not the case here, in some places her seams were barely 3 threads in and the fabrics seams didn't match up at all. The top fabric and the bottom fabric were worlds apart. You could see that with just a little bit of use, the quilt seams would just disintegrate and shred in no time. I was very surprised that her sewing was so slipshod. As I said earlier, we all sew so differently.