I went to town on looking up as much about Atmosphere as I could this weekend.
1) The rendering engine is the most sophisticated I've seen. I'm totally impressed with the lighting.
2) Performance is slow as a dog on a hot July sidewalk on older machines.

What's everyones take on real multiuser capabilities? My take is:
A) If I wanted to author interactive games, I think Blaxxun/VRML might be better only because of preformance speed.
B)If I want to take visitors through a beautifully rendered, albeit slow, world (such as architecture) then atmosphere would be a better choice.