I am novice in the World 3d, but one think is common in all 3D programs. The time expending in renders.
I am waiting for the unforgetable day when someone create an efficient render system which you could check your work quickly before making the final render.
Actualy this process expend to many time of artists and ask for enourmous volume of memory, and sometimes it can be broken during the process.
If Blender 2.5 solution offers this kind of new I think many people will make a party to celebrate this day.