so funny,
I just read the comments just before me and I was saying
"wow, this guy is pretty hard with the game... directly asking about the game lenght or the multiplayer ..."
later, I saw it is was starcraft ...
to answer you :
game lenght : we dont know
multiplayer : I dont think so
and yes, Mass Effect will have 30-40h of main game + 20h of "extra quest"
are you happy ?
Time to Work !