I just installed the pro kit, it's pretty straight forward and relatively easy if you follow the supplied directions. The kit took about a week to arrive, but I live in Arizona so the ship time was only 1 day.
A couple things I didn't see mentioned while skimming through the thread:
1. If you are having low volume issues and you are using the 3.5mm audio jack on your mp3 player, make sure the volume is turned up high on the actual mp3 player.
2. I was able to run the rca to 3.5mm cable under the faux wood side trim on my legacy. I have it coming out about an inch back from the emergency brake release button. It's not the most convenient location but it works without having to do any drilling/cutting.