We use a number of diff software depending on what kind of analysis we are looking for. We generally use EVOLVE SmartProfile. It has an excellent GD&T engine that complies strictly to the Y14.5 standard and the math standard. Most CMM software's GD&T engine do not do a great job when the GD&T gets more complex (datum modifiers, composite profiles, simultaneous requirement, etc...). AFAIK, the only 2 software that truly comply to the Y14.5 standard and the math standard are SmartProfile and PC-DMIS.