I can't much of course, what with it being a closed beta, but what I will say is that it's so far been a fun experiance. To put it into persecptive;
I played WoW for a few hours and was bored stupid.
I've played WO for a few hours and I want to play more. Unfortunately the client is a bit broken in Vista atm, so I'm having to hold off playing until the next patch to see if that fixes things.
I think the main way that it is different is with the start up; in something like WoW you basically have 'go here, kill x things and return' quests, many often sending you to and from the same location. Thus far with WO I've had a sense of moving forward as each 'mission' has sent you to a different area, or your movements have made sense.
There is also some scripted RvR events you can join in with, which automagically group you with others taking part in it.
So, so far, WO has been pretty fun; when the client works again we'll see how it progresses, but if it stays as fun it could be the first MMO I buy since Eve.
*cry*