3ds Max 6 is the the new "evolved" version of 5 as discreet would say. They added even more features than they normally do when they come out with a new version. Luckily, all versions of 3ds max use the same "*.max" format. The only thing is if you use old version files on six then you have to resave the data so that it may update to version 6 "*.max" format. In other words you can older and/or newer files even sweeter. I am happy about the fact that discreet ships 6 with not only reactor, but also with mental ray.