IDL is legitimate global illumination with accurate occlusion effects, things that were faked prior with a lot of tedious adjusting. Highly realistic. SSS emulates how light is absorbed and scattered by various substances, it's possible to create very realistic renders of various materials. Skin, wax, anything that is (semi)translucent. It's not that difficult to get a handle on these things with a some reading and testing, there's also many tutorials and discussions, documentation, scripts and freebies relating to such that makes the implementation of these advances easier. Snarlygribbly's EZSkin (free), Bagginsbill's EnvironmentSphere (free). All of these are pretty much standard operating procedure in Poser now. It's the nature of the beast in this medium to have to digest copious amounts of tech info in order to best serve your vision; Once you have this knowledge at your disposal you'll be able to readily manifest your ideas in a more intuitive way.

_Don't see why most Poser legacy content wouldn't work in current versions of Poser. If it worked in Poser 7, should work in Poser 9. There are exceptions and differences of course depending on what kind of content you're talking about, scripts in particular. Things like props and figures... Totally compatible. Many times you'll just find that more recent developments have made older content obsolete, sub-par or in need of an overhaul.