Food service sanitation courses will tell you 'no, not safe'.
If keeping it though, heating to 160* and holding at 140+ (if I remember correctly) or so for a few minutes will kill most of what has grown though.
From personal experience around my house though, I'd eat it without fear. I've forgotten and left things out overnight many a time and never gotten sick. Granted this is not the 'official' word and definately not okay for a restaurant, but what you can get away with at home is normally pretty liberal (mayo products being the big exception).
Yeah, just eat it. My little brother bitches me out now all the time because of his nutrition courses, but I've been eating food that's been out for years (and chicken that I bought more than 5 days ago), I the only place I ever got food poisoning was at Carl's Jr.'s- supposedly where food is "fresh."
low 80s is too warm for that length of time. chuck it.
Note: you can recook it, and if you eat it, there won't be zillions of toxic critters in it that will infect your gastrointenstinal tract. However, you will still eat a degree of toxic by products that the bacteria generated whilst growing in the petri dish...er food plate. Eating that can make you so sick you will yearn for death, just for the relief of not puking every 3 minutes for 48 hours.