vipers are notorious for the lack of brakes. so if you are planning on driving on road courses be careful. other than that there isn't really wrong with them.
Not only that but the car is very unstable under braking at the track.
My mom used to have one when it was the car to have...
I am not a pro but I do have good experience at the track and if you ask me the car just had to much torque and felt light on the tyres and nose heavy.
We took it to the track at Cressen several times and it was all over the place.
When she sold it I wanted her to buy a Lotus Exige where I could really have fun at the track but she did not... She bought a Chevrolet SSR. She kept it until the new wore off of it and now has a Vette. I think the Vette has been her favorite of them all. Note: She lost alot of money on the Viper.