So I had that vibration problem with my 07 5. The service department changed everything except the engine and the problem was still there. I had aftermarket rims that they put on and they said it was that. So they put on stock rims and it got worse. Anyways.....car was in the shop for over 2 months they did not want to work with us so i wrote mazda a stink letter and all of a sudden the dealers wanted to help us. So instead of filing a claim they switched it out for a 08 5. Put all my goodies from my other car to the new vehicle. But one problem.......my 08 5 has a vibration in the steering wheel. I refuse to go through this same problem again. This vibration will find itself at a HONDA dealership real soon......
you got your '08 now, and it's vibrating? LOLZ. I guess these cars are just kinda crappy. Too bad because some aspects of the car are amazing. The engine is quiet, smooth, and flexible. The tranny is decent and shifts nicely. The handling is nice. It's great on gas. Roomy and versatile.
In the end, it's hard to achieve perfection in an $18k car.