Season 1 is very different from the other seasons. It focused on specific people that would compete in large competitions.
Season 2 started out w/four contestants, host, and three judges. Contestants would have to make something like whole hog, brisket, short ribs, etc. But there would be a curevall thrown at them. They would have to stop and make something like frog legs, catfish, or something else non-BBQ related. The person with the worst dish was eliminated. Then an hour before the remaining three were supposed to turn in their BBQ dish, they were thrown another curveball by making a side dish like coleslaw, potato salad, etc.
Season 3 on was very different and I was glad they changed the concept! It was a mix of season 1 and 2, the best of each. The judges are much better, no host, and no more curveball challenges. Understandably, contestants would be frustrated losing over something like catfish or alligator instead of the reason they were there, BBQ. Same with doing away with side dishes. Also, judging is different. They do the numbering system where the judges don't know what belongs to who (like season 1) but the contestants get to watch the judges critique on a TV (like Johnny had arranged at the end of season 1).
All in all, it's a fun show. My favorite of the originals is Johnny Trigg, but I added Moe Cason after season 2 aired. I very much recommend the show.