I took our old Honda Hatchback to Laguna Seca for a November 2011 race. A great chance to race at LS and with three drivers for one day, and $1000 it was a good deal for us. We had tires and didn't have to spend anything on the car. Our guy screwed up the AVI calc, and with the header (+$50), and rear coil-overs and sway bar, we were over the $500, so we had a couple penalty laps to start with. But in our case, we didn't care, we were there to race the track.
The 2 hour drive stint rule kind of screwed us up a bit and we actually had one guy go over the 2 hours (7.5/3 = 2.5), cause we for got about it until we were reminded. The second guy hit a berm, damaged the car slightly and got BFed for the noise. The left front strut top shear through its mount and was banging the hood and the strut tower every turn and the workers would hear it. Pitted didn't see it, they let us back out. #1 driver drove short and then at the end with the busted strut banging away to get ~2.5.
LG limits the track to 30 or 35 cars, and it was great not having the normal 100-175 cars of Sears Point/ Thunderhill/Buttonwillow out there as excessive traffic. We ran clean laps, pushing hard and had to deal with some faster cars every lap, but not every corner. We were one of the slowest cars (125 hp 1800# honda), but we finished 16th/35. we beat an EC BMW 3 series that had some fast but bad drivers, who kept spinning off track. As far as I know there was not one car to car contact the whole day, and all of the drivers I thought were very respectful of each other, while still running fast. I thought the corner diving wasn't there, passing excellent, and A**hole factor non existent.
Chump is definitely more about racing, and racing fast. The rules are definitely a bit different and you can get slammed by the AVI and add ons with the parts swap spreadsheet, especially if you've raced Lemons a few times and upgraded due to low residuals. Chump allows rebuild parts, but no real upgrading. You need to build it right the first time. That said in my one day experience, I saw what I would consider more cheaty cars running with fudged AVIs to allow more upgrades. But that is my opinion.
Go do it, and find out for your self.
Dudes Ex Machina:
https://www.facebook.com/dudesexmachina?Everyone who has ever built anywhere a 'new heaven' first found the power thereto in his own hell- Frederick Nietzsche