NeuroVR is a virtual reality system that has been developed for clinical use. It looks impressive and I'm in the process of trying to get a VR headset to test the deep immersive element of it. Although the software itself is free and the graphics are (fairly) impressive, I don't think it rivals Second Life in any way. HOwever, the system does allow the user to plug in a set of LCD goggles for that extra boost of virtual realism. One of my big problems with Second life is that unless you have a massive monitor and sit very close one's peripheral vision tends to diminish the experience. I'm aiming to get a deeper immersive experience to test some experimental paradigms I'm working on at the moment. The NeuroVR platform itself is pretty basic but it does have a hearty clinical following (CBT, phobia treatment, etc) so I think we'll shortly be able to cross platforms with this technology. Here's a presentation about it.