I have the 4000NEX and I have to say that the Pioneer/CarPlay experience has been very disappointing. I bought the unit (almost $700...ugh) after CarPlay support was announced, but before the CarPlay compatible firmware was released. When the firmware finally came out (much later than originally claimed) it was limited to only a few Apple Apps and Pandora. Since I have no other experience with CarPlay compatible head units, maybe that's just how it is. I thought maybe more features would come with the iOS 8 update/iPhone 6, but the Pioneer firmware was completely incompatible with iOS 8 (and therefore the iPhone 6). Pioneer didn't release their iOS 8 compatible firmware update for a couple more months after Apple's iOS 8 release. Even then, and to this day, it just doesn't seem useful. Startup takes ages, browsing my tens of thousands of tracks in iTunes is slow, I don't use Pandora, I prefer Waze for nav...blah blah blah.
So, I just connect my iPhone via the normal bluetooth audio connection and it works great. I've got it mounted directly over my rearview mirror for Waze nav and it will briefly mute whatever audio I'm listening to if I've got alerts turned on. I've got a button on my steering wheel to poke Siri so I can tell her what I want to hear. I can also tell her to send/read texts or make calls. In fact, ANY audio source I can play on my phone will play through the HU via bluetooth. And if I've got passengers, it's way easier for them to take over the bluetooth audio control than it would be to swap a CarPlay device, which must be connected to the one CarPlay dedicated USB input.
I haven't even bothered to try the AirPlay feature recently; maybe things have changed? I see Pioneer released another firmware update in December, but honestly, I am struggling to even give a damn. I think I'm over CarPlay. Has anybody out there had a positive experience?