I drive an 04 A4 Cabriolet, and I finally got my Pioneer Avic f90bt installed last week. It has been sitting in my closet unopened for about two months...

As far as all the installation necessities go, I used this posting as a reference:
http://audizine.com/forum/showthread.php?t=175690

I had Best Buy do the installations (I am beyond clueless when comes to cars) and they charged about $200. The thing I like about Best Buy is there is a lifetime warranty on the labor and when I go to sell the car, they will remove this receiver and reinstall the factory one at no charge!

I'm not completely happy with the dash kit only because it looks kinda cheap, but I am probably just nitpicking... you can't really tell in these pics though (or maybe you can) and some people might not even be able to tell at all. I may eventually have an auto shop fabricate a custom dash kit for me... but don't really have the $$ for that now.

 

yea that dash kit can always be customized looks good