The thing that always bothers me is that although we talk about the width of the seam, you shouldn't measure the seam you measure the resultant patch. Sew with the size seam that will result in the right sized block. As mentioned, there are some patterns that as long as your seams are all the same you'll be good. Other more complex blocks require more precision. It takes the same amount of time to sew the correct seam as incorrect. I'd rather spend a few minutes fine tuning my seam at the start of every project than lots of time stretching, easing or ripping blocks to fit.
Achieving an Accurate 1/4" Seam Allowance