Ill just add on to what
Nique303 has already said - The Metra kit is actually pretty slick for the price. There is a whole lot that goes into retaining factory controls, and Metra pulled it off without a hitch.
Having installed a few of them, I have made every mistake one could possibly make. Likewise, I have always been able to find the solution. I strongly encourage anyone contemplating paying for an install, give it a shot yourself. You will save big money that could be otherwise used for more mods.
The install on my car was about as complex as it gets. I went with the DNX9960, which requires mounting a new mic, voice control switch and satellite/GPS antennas. I also did new 6 3/4" components in the door, 6x9 coaxials in the rear deck, 400 watt main amp, 2 12" woofers and a 1000 watt sub amp. I'm very very anal about things being done right, thus my refusal to pay some shop to do a hack-job.
In reference to losing your vehicle controls - It is not entirely accurate to say you "lose" them. You can retain them with a simple module that plugs into the Metra interface. See pic #3.
Anyhow, here a few pics of my install. I opted to paint my Metra face and shift bezel to match my exterior, SIM. For some reason, Metra chose to use blue as their button color. In effort to balance the rainbow of colors that was in my car, I lit up my footwells with some pretty blue lights. I also changed to LED on my base knob to blue.