The changes that I've noticed the most in my body so far is that my left shoulder is feeling more balanced, my inner thighs feel strong, and my right hip is rotating back in. I'm most excited about my hip. I've been exacerbating negative habits that I developed from playing a lifetime of tennis. When you hit 10 million forehands with your hip open on just one side, your leg is going to be turned out. Not addressing this rotation has 100% been the source of any knee pain I've had and general tightness all around my right pelvis and low back. Ouch.
I won't get deep into it, but the turnout also affects how my feet strike the floor and that's relevant to the health and balance of my hips. It's something to consider if your feet cramp a lot, for example. I definitely went through a foot cramping phase around day 6 and 7 where it was hard to move through the Advanced System while maintaining mirror imaged feet. (Something I talk about at great lengths in class).
Completing the Advanced Reformer system requires slightly less and less emotional energy. I often don't want to do it because I'm tired or have errands or whatever, but I never regret it once I start. I'm excited to complete the 30 days.