Agree, looking into moving the stock radio into the cubby and mounting the tab there, can do with 7" display but not 10" (have both, best choice is 7".
Point is there are many thing a tab, particularly a 3G/4G tab can do that no current factory radio can such as alarming/reading e-mail, on line traffic reports, displaying traffic cams (like this
one), find and make resterant reservations, even open your garage door from a mile away. For the passenger it can stream video from Netflix. Plus the sat-nav.
For me it can read many engine parameters, display and reset fault codes. Plus play music from anywhere and act as a handsfree Vonage/Skype telephone. New tabs can multitask. All for $300-$400 and dropping.
Until you have it, you really do not know what you are missing.
ps there are things the stock radio does better (Sirius, drive real speakers, Uconnect, play CDs) than a Tab, could just get an amp but is easier to use the factory radio/wiring for audio. For this having the 130 is a plus.
My base right now is a Samsung Galaxy 2 7.0 since it has built in GPS and Accelerometer, Bluetooth and 802.11 plus more I/O and storage capability (expandable) than an iPAD. Also the soft keyboard has numbers on top of the letters. I already have a 3/4G Mifi device so did not need that