One of the PC who plays in my Encounters session has a power that lets him make a stealth check to hide if he has "concealment." Last night we was behind a hard corner in a room without any other terrain effects. The monsters had their line of sight partially blocked which gave him cover. So the question came up on whether cover also grants concealment for the purpose of making a stealth check with his power. This was important to the PC because if he makes a successful Stealth check he gets combat advantage and does more damage.
I ruled that it did not because even though the monsters would have a difficult time hitting his PC with a ranged attack due to the cover, they could still partially see the square he was standing in as he was trying to hide.