The main, direct improvement she made was with my communication style. I had a tendency to explain things. OK, waffle. She helped me make it more punchy, keep the audience with me. Has worked well.
The most interesting, and affecting, exercise was soliciting feedback on how I come across. From family, close friends and work colleagues (senior, peers and juniors). And then interviewing them about it. Not sure it made me change anything but it affected profoundly how I saw myself.
We eventually got into building people skills. There were active listening skills, some mental models to help find common ground, and we talked about bad assumptions to make versus good assumptions. For example, it's usually good to assume that your co-workers don't have bad intentions.
Are you trying to find out if it was worth it?
I found it very valuable. As with any kind of coaching, you could try to work through issues on your own, but it might take you awhile. With a coach, they're there to call you out when you try making excuses and keep you honest. Also, I found that saying and talking about things out loud has a much bigger impact and weight than just thinking them to yourself.
It also helped that this particular EC had worked for about 10 years as a software engineer at my company. When I described work situations and problems, he understand exactly what I was talking because he understood some of the political dynamics of our company and technical language I was using.