I've had far more people say "That's freaking sweet!" than ask "Why?". And even if they do ask why, how is that a "problem"? It's a perfect oportunity to share the hobby.

*Navigation
*GPS Speed (OEM Speedometer is always off)
*All My Music at my fingertips (Including secured files that won't play on regular MP3 head units)
*Movies (for passengers)
*Works with virtually ANY media storage
*TV (for passengers)
*On-the-road music downloads
*Online Radio Stations
*Live Traffic Updates/Rerouting based on traffic
*Locate Cheapest Gas in area
*Dashcam Video Documentation in case of accidends/tickets
*Backup Camera (Ditto on documentation)
*Charges My phone via USB
*Hands Free Calling
*Onboard Diagnostics/Engine Management
*Surround Sound
*No disks to chance, scratch, lose, get stolen.

You can have all this, and anything else a computer can do, plus add HD radio, XM, and Serius, etc. And you only spend about what you would if you buy an in dash navigation system (OEM units cost even more). And those units don't even have any storage. And then you would still have to worry about "subscription services".

Frankly, I love it when people ask why. I tell them all that, and then ask them why they haven't done it... I have yet to hear a good answer.