My suggestion:

• Replacing missing textures, like Lightwave: if a texture is missing, ask the user to find it... and don't search the entire drive, either! And, when the texture is selected, use that folder to look for the other textures. Stop asking for the "MilBody.jpg" file when I've already found it 10 times already.
• Platform-specific versions. Enough with the "we wrote it to be translated on Windows and OSX" bs. Write it proplerly for Windows to take advantage of the Windows Dialog Boxes (where the OK buttons are always in the same place). Stop re-inventing features to be "cool" or to take the "easy" way out.
• I don't care if P6 includes the latest 3D atmospheric Phong-Z native-mesh rendering render engine if the program crashes whenever I click in the Face room! Fix the bugs THEN add new features.
• Put back all the plug-ins that came with Pro Pack, but were lost in P5: Lightwave, Vue, etc.
• The long startup time issue: why does Poser take so long to start. If I start Lightwave, it's opened by the time I finish reading this sentence. What makes "lowly" Poser take so long to open? Let's see what happens when the Poser Sux survey comes out.