While Blue Mars is very much still in Beta and rough in many ways, there's one feature already in place that's really striking: The ability to detach your camera view from your avatar.
Normally, the camera stays just over your avatar's shoulder, as if you're looking over it (which is a default perspective for most online worlds and MMOs.) By rolling your mouse wheel, however, you can change that view so that the camera gradually moves away.
I'm used to having this ability in Second Life, but as I recall, with SL the maximum distance the camera can be from the avatar is around 100 meters. With Blue Mars, the maximum distance seems more like 500 meters, enabling you to move in a split second from just above your avatar, to looking at it high overhead. (As depicted at left, in a Blue Mars city called Digital DNA.) This gives you the instant ability to see yourself in relationship to the wider geography, a feature I have to think Blue Mars developers will want to use in the future. (Instead of creating a separate map display, for example, you could make a City's road marks visible in this God's eye view.)
But I like this feature most because it's almost a philosophical ability: With several turns of the mouse wheel, you can literally see just how small you are in relation to the world around you: