This game is actually sick! I torrented it years ago and loved it so much that I bought it. Simple, yet challenging gameplay that's big on spectacular vehicular destruction. Satisfying is a good word to describe this game.
Second one is where its at, its basically just the first one but looks a hell of a lot nicer, and had a better OST in my opinion. If you enjoy either, Flatout 4 Ultimate Carnage is pretty good to, and stays true to the series. Flatout 3 is awful.
We played the derby mode of the successor (FlatOut 2) to death at LAN parties. Great game. Never played the first one though I think, so I'll check it out.