I used Ray "Nightmare" 3d (demo), 4.1, and 5.5 Everything before 5.5 had severe stability problems, frequently corrupting the file during the crash. Even 5.5 had interesting modelling problems. It may have been the platform and OS I was on, but the meshform modeller was excrutiatingly slow to react. You could have lunch during the time it took to weld two halfs of a model together. The upgrade path to Carrara was a little bit over a hundred bucks. All the modellers are improved. The addition of subdivision surfaces alone, (and addition of creasing to subdivision surfaces in 3.0) is worth the money. The old windows of Ray Dream are replaced by multiple windows with reference images, responsive camera controls, display options. Plus everything else Brainmuffin mentions...particles, boning, the tree generator, the cheap plug-ins Anything Grooves (displacement mapping) and Anything Grows... If you have to stay with the Ray Dream series, go to Carrara as soon as you can scrape up the bucks. You'll earn back the money in time and aspirin within days.