As an app developer, I've always been following the new Mac Pro (usually shortened to nMP, as opposed to the cMP, where c stands for classic). For portability reasons, clients usually give me a retina MacBook Pro to work on, but the Mac Pro is a desktop computer. Thus it offers all that desktops usually offer: more power.
If you're a desktop person then for some time, the Mac Pro hasn't been the first choice; usually the 5K iMacs would be a better choice. App developer Marco Arment explains why: The Retina iMac versus the Mac Pro.
And then there's the fact that the nMP couldn't really be called "new" at this point. Both the CPU and the GPU are pretty old tech. And its SSD is easily beaten by the SSD in the 2015 rMBP. It hasn't been updated since its release end of 2013 and the MacRumors Buyer's Guide maintains a disheartening running tally since its last update.
For 2016 however, the stars might align and Apple may give some love to the nMP. Over at the MacRumors forums, enthusiasts have been speculating and there has been long-running thread with the subject Will there be a new Mac Pro in 2016. User Stacc gave an excellent summary of that thread which explains what we can expect of the new Mac Pro.