While working I started streaming mid-race, and listened more than watched. Commentator was knowledgeable and presented information really well. Was baffled who it could possibly be, and pleasantly surprised when I saw it was Rupp!
He is amazing. He knows how to be exciting for casual fans while keeping us running nerds happy at the same time... a delicate balance. I hope he's a mainstay on the commentary teams for decades to come!
Today was my first time hearing Galen Rupp as a commentator. I have to say, I was pleasantly surprised. He was pretty good - not great, but definitely not bad at all.
I do have to disagree with a couple of posters upthread who I think are overselling how good he is at it. I don't think he's as good or polished as Kara Goucher, or quite ready for major broadcasts yet. For example, he did sort of trip over his tongue at one point, and apologized for it. You have to keep in mind the question, what would you think of his commentating if he was someone you had never heard of? Yes, I get that part of the reason he is on there is because he is Galen Rupp, and some people want to hear his specific insights based on his personal experience, but that only goes so far - to be an asset to NBC's team, you would have to appeal to people who don't know who you are, or maybe recognize your name but don't know/care much about your running resume.
But having said that, I'm rooting for him to keep at it, and wouldn't be surprised if he is able to up his game in the future.