I had recorded it, so my thoughts after finishing watching:
It was a good debate. Much more substantive and flowing than the first. Overall, the moderator was okay (some questions were biased and loaded, but I expected that) and she didn't make herself part of the spectacle like Wallace did.
It may have been Trump’s best debate between 2016 and 2020. He seemed in command, was funny and likeable at times, tough when he had to be. Much more measured and focused this time.
Biden had his moments of lucidity, and the first half or so was his best half in terms of hanging with Trump point for point. But you can clearly mark when he started to run out of gas - much more stuttering and verbal wandering. He blatantly lied quite a few times, but you could best spot that only if you knew the background of the topic. He definitely shot probably both feet off with his oil industry remark. That was a massive error, and Trump knew it - he looked like he couldn't believe Joe would actually say that.
His denial of saying he opposed fracking, then asking Trump to show the tape (which is readily available) was also pretty dumb on Biden’s part.
The comparison was more in focus last night - Biden looked and sounded old, while Trump looked quite a bit more energetic by comparison. They should have asked Biden about being possibly the oldest man ever elected, and whether he would pledge to serve one term. He wouldn't knock such a question out of the park like Reagan did in 1984 - but that's probably why they didn't ask it.
Overall, Trump won fairly easily. Did it actually affect voting decisions? Maybe some, but not a lot. People already know what they're getting. At most, Trump fans were reassured after the first debate, and Biden fans were likely a little more nervous compared with round one.