I agree that if you have a project going in Poser, you'll want to finish it in Poser most likely.  As to whether it's worth it to upgrade to Poser 9, you will have to look at the newer features and decide whether it's of benefit to you.  I've found the improvements for my work flow to be minimal over Poser 8; it does have weight map support for new Poser figures that have that (none of the Daz figures will have Poser compatible weight maps).  If you want to do your own weight mapping, you have to go with Poser Pro 2012.  If you are not a content creator it's unlikely that it will benefit you much at your stage on the Poser path.  The new versions do have prettier open gl previews and give you more of an idea of what your lighting will look like when rendered.  The new sub surface scattering feature is lovely and so is indirect lighting.  To be perfectly frank I like the lighting setup much better in Poser than Daz Studio and I think it's easier to get a "realistic" look without having to spend more money on expensive Daz Studio lighting set ups (like Reality--which isn't currently supported in Daz Studio 4 yet).

I think the best version of Daz Studio for the serious CG artist who isn't a content creator is Daz Studio 4 Advanced which includes many plug-ins that would be costly to add to the base free version currently.

I hated M3, but this new M5 will have far greater potential with the blending capable with other shapes.  Yes, as stated above you can use standard and Genesis figures together, the picture above shows the Freak 4 on the left and the Genesis male on the right.  It might be worth noting that genitalia is not included with the standard Genesis package--if you want your figures to be fully equipped you'll have to buy the Pro Bundle of those figures--or buy 3rd party add-ons.  I purchased male genitalia at Renderotica for my nude male renders--and that option will be cheaper than buying the Pro Bundle when it arrives.  The same holds true for Vicky--if you want the lower body parts you have to get the Pro package or find a 3rd party alternative.  It might be worth noting that Vicky in her earlier versions never had female external genitalia, so at least they are offering the option now.  If you want to get more of idea of what Genesis can do I reccomend watching Daz's videos about it and playing with the free version as I already suggested.  For that matter you can download a trial of Poser 9 and give it a whirl too--I can't tell you how many times I'd wished that I'd done that before purchasing new software.