Ok, well I've been playing around mainly with the lights for a couple of hours since I have no content yet (download is painfully slow) and I like the results I'm getting with indirect light.

Renders seem superfast to me compared to Poser 7 - i'm on a quad core and in P7 after each section finished it would just get slower and slower with fewer cores being used.   The P8 renders seem to go by fairly quickly even with near perfect quality settings.

I'm in two minds about the Library - yes all my jam-packed runtimes load much much faster but navigating it is a pain.  First the tiny previews don't allow me to choose what i want unless I preview them all at a larger size and since I make extensive use of subfolders in categorizing stuff it's a pain to navigate back to the beginning of the main folder to exit it.  

Using the navigation arrows from the keyboard has no effect - works for 4 or 5 instances and then mysteriously stops.
I can see myself using P7 to set up scenes and using P8 for lighting and rendering only.   Unless of course P3dO Explorer will work with P8 as well since that's what I have been using up to now to navigate my libraries and open up files in Poser. I have yet to find a better solution to that.

As for the new content, I can't say since I haven't downloaded it yet but I'm pretty sure I will use it about as much as I've used P6 and P7 figures/content - a couple of weeks after getting them and then they started gathering dust.

As for the new UI I really don't care, I can work in that just as well as I could in the previous versions, never saw what the big fuss is about.  I think maybe I gain a few pixels in the preview window's width when it's docked but that prevents changing the window size (which is something I often do) so I keep it floating for now which really amounts to the same size window I had in P7. 

All in all I'd say, for me, the high points are the lights and rendering and I hope future service releases will enhance that.   Also looking forward to what developments we'll have with python scripts.