I was hooked on FlatOut for a week or so. It's a really nice game, though it sometimes feels a bit random (especially with regards to how the car reacts to collisions).
Overall, I think
Cross Racing Championship is a better game. It's definitely less glitzy, but the racing is more satisfying and it feels a bit more consistent. Well worth a try if you like FlatOut.
Oh yeah, and I'm looking forward to FlatOut 2, though I do wish Bugbear were working on Rally Trophy 2 instead. Until Richard Burns Rally came along, RT was the best rally game available.