By now, virtually everyone on the planet groks the whole Unit Test thing and even writing the unit test first, but Pair Programming has always been the toughest sell to management. Many times I have gotten all of XP adopted at a company except Pair Programming. Management's fear is that they instantly lose 50% productivity. It's a shame because exactly the opposite happens. This study, among many others actually show a big increase in productivity that comes from the synergy of ideas, instant code review, and refactoring on the spot.
The hardest part of getting any new idea in place is overcoming the built in biases - both of management and of developers. I've had some success using the "two heads are better than one" analogy - but I've not actually tried to promote XP into an organization, either.