AskMrRobot’s blog has a great guide for Garrisons (thank you Ask Mr Robot). I knew almost nothing about them, but after skimming through the basics I think it will be a major feature I’ll use in Warlords. Truthfully I can see garrisons being played on many alts and mains from day one, to acquire what they have to offer. It appears that Garrisons will have a straight up advantage to using them (very much like the Farm in Mists) and a wide breadth of game-play too. The fact that you could have a main with a raiding garrison, then alts also generating gold and materials is excellent.
Impressed, especially the chat sheet at the end which shows which garrison feature selections are better for raiding, farming, alts, or pets. The guide indicates that a full garrison will cost around 39,000 gold. Holy snap!