The 2nd post in this thread covered the UI issues succinctly - not that the original Kai Poser 4 UI was ever rational ;-)

Indeed Poser 4 & Poser 4 ProPack were the last versions designed as a whole.

But the real problem with post_P4/PPP version is that not only is the UI grafted on, the new features are literally grafted on too. Look at Poser running on Linux, where Curious Labs' programmer couldn't mask the Taskbar display, and you'll see that the new Document (posing) window, the Dial Palette and the new Library are EACH separate tasks! This was obviously a problem at P5 release, with respect to dial turning response, and it has only become less of a problem since because PC's have got fast enough to mask that ludicrously poor design choice. And a candidate reason why those of us still running same PC's as when we used P4/PPP still prefer posing in P4/PPP.

[ An analogy would be today's cruise ships and oil tankers doing away with their direct control of the turbines from the bridge, and going back to the old bell system where the engines are adjusted remotely in the engine room - do-able on the open seas perhaps, but try finessing a docking! ]

And beyond the above, whatever programmer designed/implemented the new-in-P5 circular menu on the Library window deserves to be unemployed, at least as a programmer :-O