The primary benefit of using shift instead of move, is this:
No Opportunity Attacks: Your movement doesn’t provoke opportunity attacks.
Despite the above, can shifting still trigger immediate actions such as immediate interrupts and immediate reactions which are triggered on movement?
Yes.
A shift is very well defined in this question: Shifting
Shifting allows for combat movement with out trigger opportunity attacks, but it does not say anything about hindering immediate actions that are not OAs. By definition this means that immediate actions (out-of-turn things) still apply.
As long as the reaction being triggered is not an opportunity attack.
DEFINTION - (taken From DDI): Just for reference.
OPPORTUNITY ATTACK: OPPORTUNITY ACTION
Melee Basic Attack: An opportunity attack is a melee basic attack.
Moving Provokes: If an enemy leaves a square adjacent to you, you can make an opportunity attack against that enemy. However, you can’t make one if the enemy shifts or teleports or is forced to move away by a pull, a push, or a slide.
Ranged and Area Powers Provoke: If an enemy adjacent to you uses a ranged power or an area power, you can make an opportunity attack against that enemy.
One per Combatant’s Turn: You can take only one opportunity action during another combatant’s turn, but you can take any number during a round.
Able to Attack: You can’t make an opportunity attack unless you are able to make a melee basic attack and you can see your enemy.
Interrupts Target’s Action: An opportunity action takes place before the target finishes its action. After the opportunity attack, the creature resumes its action. If the target is reduced to 0 hit points or fewer by the opportunity attack, it can’t finish its action because it’s dead or dying.
Threatening Reach: Some creatures have an ability called threatening reach. This lets them make opportunity attacks against nonadjacent enemies. If an enemy leaves a square that’s within the creature’s reach, or if an enemy anywhere within the creature’s reach makes a ranged attack or an area attack, the creature can make an opportunity attack against that enemy.
Published in Player's Handbook, page(s) 290.
Shifting doesn't provoke opportunity actions, with the exception of some creatures that can mark have stipulations that if you shift away from them they can still attack you (much like the fighter's mark ability). Also I've seen some newer creatures in the monster vault that have similar abilities if two or more of them are adjacent to you. But in general, shifting doesn't provoke.
