All my recent DAZ purchases install into My Poser 5 fine, what is it that they are not supporting?

DAZ has gotten a little better about supporting P5/P6, but it's still a crapshoot.  My latest encounter with their "stuck in PP" time warp: the animals pack from March Madness.  I can't complain too much, given the price I paid, but I still found it aggravating that the bump maps didn't work correctly in P5/P6. 

That's the usual problem with DAZ products.  The bump maps don't work correctly in P5/6.  Newbies often don't realize this, since they often don't even go into the Material Room.  But if you look, you'll see the bump maps attached to Gradient instead of Bump, or not connected at all.

Another problem is backward-facing polygons/intersecting polygons.  The P4 renderer handles these okay, and I assume D|S does, too, but Firefly does not. 

Two products that have this problem: the Wedge 2 hair, which renders with ugly black streaks in it, because of the tube-like construction of the bangs, and the fairytale bassinet, which ends up with dark streaks in the skirt, I think due to intersecting polys.  You can sort of fix these problems with P6, using "normals forward," but P5 users are often out of luck.  (Though sometimes you can do things with the Alt_Diffuse node.)