I got the 1 shot J&J last week. Got it around 3pm. Injection site burned for about 2 min and then no other effects from then until I went to sleep. The next morning I woke up feeling a bit more like fried ass than normal. Mostly fatigue, aches, chills, heat flashes - I am very lucky that I work from the house still, so I was able to just lay down and rest a couple of times. It was 99% gone about 24 hrs after the shot. I had 1 more mild wave of feeling hot for no reason that evening, and not the greatest nights sleep, and then the next day my arm felt a little sore. My wife experienced much of the same with her side effects lasting a little bit longer. Brother in law had similar waves of fatigue after his 2nd shot of the moderna.
If that's a taste of what the virus has in store, I'm glad I got the shot and not the real deal. Not being able to breathe on top of how that made me feel - no thanks.