Well Centrafuse has phone control built-in but it's not doable as a standalone program ie. you must use Centrafuse. Works flawlessly with my windows mobile phone. The only problem is the echo, which for now the only reasonable method is to use a hardware based solutions like an echo canceling sound card. I've read that Centrafuse is patiently awaiting a software patch from Bluesoleil (the developers of the bluetooth stack imbedded in their program) and that should take care of the problem.
Just a little thought for your expectations tho (as you are not the first person to raise this type of viewpoint).... car manufacturers dedicate time, effort and lots of $$$ to solve this problem therefore it cannot be compare to a hobby industry such as the car pc. Let's face it, there's not a whole lot a people who would find a need to control their cell phone from their PC as PCs are usually used in environments where just using the phone directly is more convenient.