I know a lot of people have posted about these but I thought I'd share my $.02.
The install was really easy so no worries there, the bolts only cost me $17 and the install honestly took 10 minutes. Here are my impressions.
1. The vibration at idle isn't too bad, you can only feel it in the steering wheel.
2. With the A/C on the vibration is noticable in both front seats and the steering wheel.
3. When taking off in 1st gear there is some vibration and a noise that my girlfriend says "hurts my ears, but not really hurts but you know" you can take that for what it's worth to you.
4. Took care of the downpipe hitting problem.
5. Car feels "cooler" to drive because it feels like you're actually attached to the car when driving.
e-mail me with questions.