OK guys, here it is. Took me 75 hours off and on over 3 months to get this done, but it's finally complete and I absolutely, positively love it. Gives me 100X the functionality of the OEM system.
Besides having my full music library, plus Spotify and iTunes Radio and all of the other cool things, thanks to iMessage my text messages will also pop-up on the iPad simultaneously when they are received on my iPhone and I can respond to them from the iPad via Siri while driving.
And no, I don't lose any functionality not having the 7" OEM PCM display. Everything my 7" OEM display controlled can be controlled from the multifunction TFT display next to the tachometer with the stalk. Zero functionality lost. 100X functionality gained.
I think my favorite feature has to be the Dark Sky app though... it has super accurate weather radar down to a few feet and will provide a pop-up alert with tone 5 to 30 minutes ahead (I can set how much notice I want) of whenever it's going to rain at my location. So if I'm out and about, my car will tell me ahead of rain and I can get home before it starts raining or put the top up if it's down so a rain never catches me off-guard.
Also, the iPad talks to Garmin GLO GPS unit (wired into switched power via the fuse box so it's always on when the ignition is on) mounted at the front of the dashboard at the edge of the windshield via Bluetooth and what that does is give the iPad incredibly accurate GPS positioning. Whereas the iPad alone updates its GPS location once per second, the Garmin GLO allows the iPad to update its position 20X per second and give an accurate location down to 3 feet. So this iPad is even more accurate for GPS navigation than most OEM car nav systems.
I know some of you guys will want me to create a DIY tutorial and originally I was planning on doing that, but frankly I'm just not going to be able to. To create such a guide would take me countless hours (realistically, probably about 10 or 15 hours to go through all of the photos and write up all of the instructions and put it all together). It was a learn-as-I-went type install and there were numerous iterations of things. Had to cuts countless different pieces of trim and brackets so that the iPad would fit just so. It fits perfectly and everything is secured perfectly and everything functions perfectly, but it was an almost crazy amount of work. I thought it would take 6 or 10 hours going into it and it ended up taking 10X that long.
Porsche iCar - iPad mini Retina installed in 2014 Porsche Boxster - YouTube