My Precious Darkness

I'm wondering at the moment if the following cards are an essential building block to many of today's decks:

4x Hypnotic Specter
4x Sword of Fire and Ice
4x Will-o'-the-Wisp

These 3 cards are so powerful, and have such great synergy its hard to think of a deck with swamps in it that doesn't want to run them. I'm sure pretty soon I'm going to be adding (and replacing SoFI with Jitte) :

Dimir Cutpurse 1UB
Creature - Spirit (r)
Whenever ~ deals combat damage to a player, that player discards a card and you draw a card.
2/2

This has to be one of the best creatures I've seen printed while I've been playing magic.

Has anyone noticed that all these creatures are spirits?