I have the Pioneer 4100 since it was introduced. I replaced a disk based Eclipse unit with it. I love that it uses Google Maps, and that they are always up to date with traffic info.
I love that Pocketcasts is supported as I usually listen to podcasts when driving. Phone calls are excellent quality, and the mechanism for listening and replying to texts works fine.
For me the voice has pretty much been spot on.
With all that said, I think your experience will be dependent on what phone you use. Many reports of issues with crufted up versions of Android (Samsung, LG), but my Moto and Nexus phones have all worked well with it.
The only frustration thus far is no Waze, Glympse, or any driving apps like Automatic, Dash, or Torque. Waze said they were super close last year but have been silent about it since then. No word from any of the above devs, so I wonder what kind of hoops Google is forcing devs to jump through for this class of apps.
I also wish I could see notifications from some other apps including SmartThings and MyQ, but I have them send texts instead so it's not a deal breaker.
So if I had something like Glympse and Dash available, it'd be damn near perfect for me. Dunno when or if we'll see these. Last time I looked, the official SDK only offered APIs for messaging and media apps, and the "car" category has pretty much been ignored.
All in all, it works well enough that I plug in more often than not (for just about any drive longer than 10 or 15 minutes).
As an audio enthusiast, I think the Pioneer is pretty good at what it does, although the interface leaves a lot to be desired. It supports hi rez files, and has pretty good control for dialing things in. It is likely it would be an audio upgrade to most stock units it would replace.