I have a Samsung Galaxy Alpha phone, which I have come to really not like at all. It has had many issues, including simply not working for more than an hour or so at a time on the Optus network in Australia (an insider at Samsung Australia confirmed that it's a known issue).
I waited for the launch of the Nexus 5X and 6P in late September 2015 to see if I wanted one of those, but ended up ordering an iPhone 6S+ after the Google announcement. However, I'm still very happy with my employer supplied Nexus 5.
I really hate the Alpha now. It's slow, it's aggressive at terminating apps in the background in a way that my Nexus 5 simply doesn't, and today it killed (well, rendered unconscious) the radio head unit in my Renault Megane RS 250!
I've used this phone with the bluetooth in this car for 6 months without issue. Today though, while I was driving I went to switch from AM radio to bluetooth. It wouldn't change. I stopped the car and shut everything down - didn't fix it. I turned the radio off, and then it wouldn't turn on again.
I rang Renault (North Shore Renault at Waitara, to give them a plug, because they fixed this for free without an appointment), and the first question asked was "Do you have a Samsung phone?"
He advised that if a Samsung phone tries to download its contacts to the car, it will sometimes crash the head unit. The phone asks if it can download them during the pairing procedure, and I have always permitted it, despite it never actually downloading them (which is a fail all by itself).
So 15 minutes in the workshop for a reset of the head unit, and it's working normally now. Renault cleared all the bluetooth pairings, so I made sure when I paired it again that I cancelled the address book download.
Yet another black mark for Samsung and the Galaxy Alpha - although the service manager said that all Samsungs including the S5 and S6 do it as well.