I had a bit of a look around in Blue Mars. The idea of a Second-Life-like world in pieces with the mighty CryEngine technology holding it together is very appealing. So far it is all very underwealming, looking far too much like Second Life. But the potential here is huge, as we adopt more and more use of engines like CryEngine2 (and any moment now, CryEngine3) here in FBE, I can see significant value in approachable persistant worlds built in this technology for virtual gatherings, simulations and visualisation.
There are certainly some nice elements in what people have creted so far, but I have hopes for far better. The Caledonia site has notes on creating content for Blue Mars using sketchup etc and here are some images from Eddi Haskell's blog post covering New Venice:
[New Venice on Blue Mars via Eddi Haskell's blog]