Poser 9 will support M4 natively, and M5 using the DSON plugin from Daz. There are still issues with Genesis characters in Poser, but they are clearly working on it. It works now with some limitations. (I don't use it personally so cannot point out specifics, but I know from reading other threads here, many users are finding it useful.)

Poser 9 is SO superior to Poser 7 that even if M5 did not work in it, it would be worth the upgrade for the addition of Sub Surface Scattering and other improvements to the render engine. You will not believe how easy good lighting becomes using the IDL feature (along with bagginsbill's excellent free Envdome.)

All scaling issues from past releases appear to be fixed.

Poser Pro is also a complete 64 bit package, which allows it to use all of the memory you throw at it (assuming you have a 64 bit operating system like XP 64, Win 7 or 8.)

The Gamma Correction is top notch and vastly improves render quality and workflow in Poser. (And believe me... I was a major critic of GC for a long time! This WORKS!) There are a couple of free utilities that you can get to really make all these features super simple. Snarleygribley's EZSkin 2 and Scene Fixer are free and automate the setup for the advanced features.

I'm running Poser Pro 2012 and would not be without the pro features.