Thanks for the replies everybody! Yeah, wasn't looking especially for "buy this model" kind of advice. Just some perspective on why the build quality of these units seems to have suffered. Although as Curt's beautiful post shows, there ARE alternatives.
And I know this is a software forum, but I've never known DC users to be shy about offering their opinions on other topics as well, given the chance.
app103, I appreciate the offer, and that IS a cool gizmo. The current Pioneer unit in my car is radio / CD only though, so I'm afraid I can't take you up on it.
For those who are interested, CWuestefeld gets at an important point. A lot of the interaction with the unit is no longer ON the unit. I'm looking at stereos that feature the new Android Open Accessory protocol which essentially turns the head unit into a remote control / speaker system for an Android phone. You can use the controls on the head unit to pause, skip ahead, adjust volume, etc. but you can also do these things right on the phone. Good for when the flimsy plastic knob breaks off I guess?
I'm going to repeat Curt's query though, and do some digging. I still think a car stereo ought to look like you could accidentally bang your toolbox against it and still work the knobs.
Plus, the dual-knob volume+tuning design is one of the most elegant and intuitive UIs ever designed, and I'm tending to stick with it just on principle. So this is not quite software related, but it is User Experience related, which I think gets me a pass for posting it on DC.