I am like Ninnie and Ducky. I like to pin everyplace a seam is to intersect or point is to match up. Not only do I match up my intersecting seams with pins but I often put a second pin 1/8 in front of the intersection because I was finding even with matching the seams with a pin my intersections were still often off 1/16 to 1/8 of an inch. I asked at a class I took once what I was doing wrong and the quilt instructor told me that the feed dogs will often advance the fabric on the bottom just a fraction of an inch quicker and if I put a second pin just in front of the seam matching pin I will solve the problem. Sure enough it worked. I still get an occasional mismatch but I am much more pleased with the results and find I do MUCH LESS unsewing if I do more pinning as I progress. I am way critical of myself and often want as close to perfect as I can get so I guess that is why I do it and I absolutely hate having to unsew.
I also pin pin pin if I have a bit of easing in to do when matching up those seams.
FF