I installed from the disc with no problems.  I did a simple (30 frame) cloth and hair simulation and neither crashed.  Both simulations seemed faster than with Poser 7.  The render engine is definitely faster.  I rendered a P7 pz3 file to see the rendering difference.  The only difference was the lighting on the fluid in a transparent glass.  The shadows looked more natural in the P8 render. 

So far, I'm loving the new interface.  I like having a big window to work in and having all the basic tools visible without having to constantly open and close the posing dials to use them and then get them out of the way.

I've added several external libraries and P8 had no trouble finding the items from the P7 pz3 files which were from several different libraries.  I have a zillion V4 character sets and a PowerPoint show with examples.  I'm looking forward to being able to do a search to find the one I want instead of scrolling forever to get to the ones at the end of the alphabet.

I haven't tried adjusting lighting or the material room yet.

So far, so good.  On the other hand, I've had every version of Poser since the upgraded version of P4 (I forget the name) and  never had any major problems with any initial version of any Poser version except, I think, 5 which was great after the first update.

For the price, I can still play with my digital Barbies and can render them faster and, once someone translates the new lights for the rest of us, make them look better.