Due to the way Poser 5 handles materials, you may need to tweak a few things (bump maps being the big one), but I use Poser 5 most of the time and almost never have any difficulties with DAZ products working in Poser 5. On the other hand, DAZ products won't take advantage of some Poser 5 features such as dynamic cloth. On the other other hand, purely Poser 5 features aren't that popular in comparison to Poser 4/Poser Pro Pack compatible items any way. (Dynamic cloth items and Poser 5 hair are few and far between, both as freebies and as commercial products.) DAZ doesn't officially support Poser 5 for a few reasons, but they do the best they can. And you can ask in their forums, and you can ask here and other forums like Runtime DNA if you get stumped on something that is Poser 5 related. Cheers!