Yes, you are in the minority. Most of us that stuck with the 5,1 are not upgrading to the nMP.
This is exactly what's wrong with the nMP. It didn't NEED to be a complete custom job. Yeah, they could have built a custom motherboard and whatever else they needed but kept the standard PCI slots. Not having PCI slots, especially for GFX cards is arguably the biggest problem and design failure of the nMP. The fact that it's ATI based is another huge failure.
If they would have kept much of the components standard, such as PCI slots, this wouldn't be an issue.
Now, if you work by yourself, or in an extremely small shop, yeah this probably wouldn't be an issue. But if you work in most larger shops, with fiber or 10G or SAS connections to external raids, the nMP doesn't fit. It doesn't integrate into the MASSIVELY EXPENSIVE HARDWARE that's already built into the post workflow. Sure you can use external TB chassis, but the throughput is nowhere near PCI-e speed. How can you recommend the owners re-invest in a complete restructuring of hardware just because Apple decided to have "courage" and remove the industry standard PCI-e slot from their machine?
I dunno, if you're an editor and you can't use your capture card because the machine doesn't have a PCI slot, I'd say that's a pretty big deal. OR, if you can't connect your $5,000+ SAS raid, I'd say that would be an issue. OR, if you can't backup your terabytes of 4K or 6K footage to tape for the same reason, I'd say you would notice.
Look at what happened at Biscardi Creative. They do a large amount of production work, and I think they are a decent example of your average Post and Production facility with a large hardware investment. After FCPX was released, they immediately switched to Premiere. This was after using FCP for many years. After the nMP was released, they switched all of their workstations to PC's. Back in 2012, Walter Biscardi was a pretty big Mac & FCP evangelist until FCPX and the nMP. They switched for the main reasons I listed above. 99% of your Post / Video / Motion GFX / Creative users need flexibility. Apple doesn't offer that any longer.