I'm not sure I agree that a fast initiative brings round 2 attacks into round 1, however it will let you to get in your attacks before the other glad which as Narol points out will help you by not getting a crit dealt against you before you have a chance to deal your own crits or skill effects. If your initiative is very low, I think you still get your attacks in that round they'll just happen at the end unless you get stunned or hamstrung which in that case you lose attacks.