We got our second Pfizer shots yesterday. After reading stories here and elsewhere about reactions following second shots, we had prepared for feeling sickly afterwards (had easy food ready to go, Tylenol, etc.). Well, we're both doing fine 36 hours later. Both of us have soreness around the site but that's about it. My wife had none after the first shot and I had some soreness then. I do think the soreness after the second shot is more intense. Fortunately, it doesn't hurt constantly, which would be irritating, but only when I lift my arm straight up, bump it, or lay on it.
Our daughter had fever, chills, and just felt crappy starting around 18 hours after getting her J&J shot. It dissipated after several hours.