The bottom line is that Apple needs to acknowledge that this is a software bug, and then just let people know they'll release a fix in the next update. It's clearly a hardware problem. My 5s that was running iOS8 connected just fine with no issues. My 6 will NOT connect automatically. To get it to connect at all, I have to repetitively select the my car's bluetooth name in the discovery, and half of the time that doesn't work. When it DOES work I can't talk over bluetooth; I can only stream music.
A friend of mine called Apple today to discuss this. They acted as if it were an isolated incident, and told him to reset his network settings, phone etc.
A) We shouldn't have to go through all of that just to connect to Bluetooth.. it's "supposed" to connect automatically once it's paired
B) That is only a temporary fix.
Apple, if you read this, acknowledge the problem and release a statement that it'll be fixed in the next update instead of making your customers angry at your deflection of the OBVIOUSLY widespread problem. Get it together !