jws,
I have a 2yr-old Toyota Avensis with in-built bluetooth - definitely not a luxury model! 😉 However I get the same problem as mentioned by many others...the phone pairs fine, outgoing calls are fine, but incoming calls are silent (unless you switch back to the car on the iPhone when the call comes in).
I'm not claiming that this problem necessarily affects all vehicles; nor do I doubt your claims that there may be android phones with similar problems (although as mentioned previously both my Galaxy S3, as well as my wife's Desire HD are both perfectly fine). Also, to be clear, I have had other problems with my S3 (and older android phones) in the past, so I'm not trying to claim that android phones are flawless!
However, what I find really frustrating is the apparent lack of anyone from Apple actually admitting there is a fault here with their phone. I know there are a few people on this board who have claimed iOS 6.1 will fix this, and if so that's great I can't wait to get it. But, what I really want /expect is someone officially from Apple to say "Yep, we know about this and we're working on the fix, should be with you in release xxx", rather than what I and others have experienced, which is Apple claiming zero knowledge of this fault and worse trying to pass the blame off onto the car manufacturers. It's just a bit pathetic, and not what you would expect from a company with Apple's reputation.