Once the bugs are worked out there should be no reason why it would be "slow" as mentioned.

The slow part is what the website said, not me. According to the creators relatives who were a testing it, the software was slow.
The compatibilty issue is exactly why I wouldn't consider PhatBox. (Kenwood & CD changers nightmare appearing again).
At least with the MK2 I can plug it into any audio input on a head unit (or amp) and not be constrained by the original head units display whatever it may be.
I strongly suspect the Phat one will have problems with the various displays on head units mainly b/c they weren't designed for this.

What's really going to bake your noodle later on; is would've happen if I hadn't said anything?