For me "squaring up" doesn't mean trimming, but rather 'altering' the blocks. If something is too big I take the seam or seams in just a hair. It usually involves sewing right next to the original stitching line. Same if the block is too small.... just resew a tad to the inside of the original seam and then take the original out. It's worth it to alter your blocks to make them fit without having to distort them. I don't like puckers and pulls in my quilt tops.
I think my background in dressmaking and alterations makes me compelled to alter blocks that aren't quite right.
