I never listened to them, but I went to one of their concerts at the Fillmore East in (I'm guessing) the very early '70s. I probably went because a friend asked me to go. What I recall is that they absolutely rocked the house. Maybe they performed some mellow country rock, but I recall a full-on rock and roll band. As I was leaving, I remember an older guy in the crowd. (I was maybe 17.) He appeared, to me, to be the epitome of a stereotypical hippie, which probably impressed me. He was saying admiringly, "they put the Dead to shame."
I don't know if this was typical live Poco or not, but it was great. I have their live album, Deliverin, and it's fine, but it doesn't pack the punch of that show. Of course, I probably smoked something that night. That's my very positive Poco memory, and I'm sure it's a narrow slice of what they were all about.