If by UNIX you mean *BSD or GNU/Linux derivatives then I agree the UNIX-like experience, as such has improved a lot, when comparing the BSD/GNU experience with the POSIX certified one.

However, I imagine that if I seat myself in front of a 2016's fresh installation of Aix, HP-UX, Solaris, Tru64... I will struggle to find any major difference from a 2006 installation, the last time I used any of them.

DTrace, ZFS, and containers should be major differences. Serious changes in how admins' jobs work have resulted from just those three. A whole cloud platform has been built when that was added to other benefit of open-sourcing one. So, Sun's OS got transformed into a pseudo-mainframe with better debugging and possibly better filesystem. I don't recall enough details of mainframe FS's to be sure on latter.

Far as Linux, Ubuntu with its software-center, Flash, VLC, and so on are much different than my early experience with Caldera OpenLinux on a Pentium 2. Which would've looked like shit with almost no apps or features had it not bricked that machine during install. ;)

So, they're not very innovative but have had huge improvements that totally change the user-experience. I mean, certain things are similar or the same especially on terminal end. Yet, we can't pretend like UNIX has sat still. It's just still not fixing its worst issues or learning from prior work as effectively as it could.

Yeah, but that is just copying the other OSes, mostly mainframe features that are just relevant for a few selected souls.

As for the desktop, yeah the experience has improved, but still no proper GUI stack in place, all is built on top of X architecture.

Nothing compared to the work done at Xerox, DEC/Olivetti or even what Microsoft does at MSR.

I came to me thinking how similar the coding experience in Mac OS X, Android and Windows or the whole OS stack is to the way I experienced Oberon back in the day.

Yes Mac based OSes and Android have a UNIX kernel, but when using the official APIs for applications, one would hardly notice it.

That was the brilliance of NEXT: leverage momentum of UNIX in lower layers while hiding it behind a sensible upper layer. Fixed up the graphics stack, attempted to provide better organization (failure = Mach), and provided consistent, good user interface on top. Maybe better API's, maybe not... never programmed Macs.

I've been saying for a while that a group needs to do this for one of the BSD's. Not just put KDE or Gnome on one but seriously reengineer the GUI, sounds, graphics, admin controls, and package mgmt. Smooth integration with high usability and good efficiency like Macs. Closest I've seen was Mint but had to ditch it for security reasons.

Yeah, I was a big Mandrake and SuSE (up to 6.3) fan back in the day.

I agree, but the pace of development of those systems over the last ten years is not comparable with the previous ten years. By that time unix sucked already substantially less. For example, SunOS 5.6, 5.7, 5.8, 5.9 and 5.10 were all released in the 1997-2005 timeframe. Only 5.11 has been released since then.