The Google Wave is still a work in progress according to ZDNet's Sam Diaz. He takes a stab at answering some of the biggest questions about the Wave.
Screenshots: Google (Click on any image to enlarge)
A conversation in Wave.
Concurrent rich-text editing in Wave.
A sample Wave extension for event planning.
Event planning, with a map.
Another sample Wave extension, for games.
How you add someone to a Wave.
Contextual spell-checking in Wave.