About the borders. I also noticed each cell is actually a space + 1 border. So you are right to say each table group is actually N+1. The extra pixel has to be

About the borders. I also noticed each cell is actually a space + 1 border. So you are right to say each table group is actually N+1. The extra pixel has to be subtracted from somewhere and I believe it's in the space between groups. I haven't looked into the cap height issue as much as you do but one thing that really bothers me and as a result the developer I work with is that Helvetica and Helvetica Neue have different top and bottom boundaries. So there are slight differences in text render on the Retina display.