I finally had some time (and a co-player) to check things out, it seems that it uses a fair share of bandwidth, the second player currently has a choppy gameplay experience (not onworkable, but more than slightly annoying). Maybe it's better over LAN, but my mother and sister are not into DX, so I haven't checked that
It's not production quality stability, but what do you expect of a V0? All in all I'd say it's usable for ~ half a mission, then it usually crashes either server or client (especially vulnerable on level changes), which I fix by starting a new game (saving is not possible, at least the menu item is missing) and loading up the last map, then cheating some weapons and skills and continuing.
If it's more stable, given time, this will be pretty damn cool
In general, the second player is less involved in the story, which is a shame, but understandable.
