I've been strongly considering this move as well -- the 160 +spell power that stacks with trinkets and no global would put all of me at 3200+ spell power for 15 seconds, plus the 15% reduction in stun is pretty nice (all though the 25% chance to resist was even better).

However the two big factors are one, the cost $140 for 4
Also, I've played alliance and only alliance on the same server since the launch of WoW -- going horde would be interesting to say the least =P