Sliver creatures you control have haste. (They can attack andas soon as they come under your control.)
7/1/2013 If Blur Sliver leaves the battlefield during combat, any attacking Sliver creatures that came under your control this turn will continue to attack, even though they will no longer have haste.
7/1/2013 If you change the creature type of a Sliver you control so it’s no longer a Sliver, it will no longer be affected by its own ability. Its ability will continue to affect other Sliver creatures you control.
7/1/2013 Abilities that Slivers grant, as well as power/toughness boosts, are cumulative. However, for some abilities, like flying, having more than one instance of the ability doesn’t provide any additional benefit.