I also do not clip the threads at the intersection, but only undo a couple of stitches in the 1/4 inch seam allowance. Charlottequilts, I have not had any come apart--yet!!
GailG, the 'pressing to the dark' is not a hard and fast rule. With a dark/light 4 patch, and following the rule that all seams should be pressed to the dark, you CAN'T 'swirl' your seams and will end up with a big bump in the center. I think it is more important to have a smooth center.