Swift & Immediate spells are becoming annoying to me. They are very useful & I like them...but as a DM, it gets annoying because they've made a swift spell that avoids any type of penalty a PC may have gotten.
PC causes an AoO? Nope, his swift spell prevented that. NPC is about to hit on his 2nd attack & will take the PC unconcious and get him out of the combat? Nope, a PC's Immediate spell acts in the middle of the NPC's action and gives himself more HP's to survive the NPC's 2nd attack.
Great spells for PC's, but not so common for an NPC to have unless you get cheesy.