Just to add to the me-too, I've not been able to get the exec to work with the 4.1.x binaries. The server connection always breaks. I also can't make the socket connection when I start the ui and exec manually. In script mode I never get the prompt. With the 4.0.10 binaries, it all works fine. Performance is reasonable. I am using this on a 500 MHz PIII, Matrox Millennium G200, 384 MB RAM, RH 6.2. But on that lowly graphics card, s/w rendering is faster unless the amount of geometry is small (i.e., I intend to replace it).
