Bear in mind that Poser Pro and Poser 8 are different product lines, as well as different generations of Poser.

The current Poser Pro is of the Poser 7 generation, with the added Pro features such as gamma correction, 64-bit render engine, background and network rendering, interfaces to other pro 3D apps, et al. It's a mature and (generally) stable application.

Poser 8 is the next generation, with IDL, light fall-off options, tone mapping, the new library, and all the other lovely features listed on the SM product pages. It's a new application and there are quite a few bugs yet to be sorted out.

My recommendation would always be to go for the latest generation of software, as long as you are patient enough to handle the bugs without resorting to axe or mace. If you really need some of the Pro features, then I would suggest you wait for Poser Pro 2010, which will be based on Poser 8.

"If I were a shadow, I know I wouldn't like to be half of what I should be."
Mr Otsuka, the old black tomcat in Kafka on the Shore (Haruki Murakami)