The most obvious change in the latest Build of the Warlords Beta is the addition of a dedicated secondary Hearthstone to your Garrison, which means for the first time in Warcraft history every player has a guaranteed second spot in which to set a base of operations, should they choose to use the feature. As the Garrison is, to all intent and purpose, instanced content without the loading screens, it makes a lot of sense to have this arrangement in place, especially if Instance servers go down and players are locked inside their Garrisons because of their 'normal' Hearthstones being bound there.
Because of the Beta Character reset I've been forced to 'start' again with my progression, but the most obvious change early on is the addition of a breadcrumb quest to Ashran as soon as your Garrison is established. As this is your Faction Hub for the Expansion (like it or not) it would make sound sense to set your 'normal' Hearthstone here for access to professions trainers etc. There is also a quest that provides you with a Garrison Follower to boot, so it is well worth taking the trip there early before you begin your journey elsewhere.
It is now becoming apparent of the amounts of Resources that will be required for individual buildings, and that choices between Outpost Buildings will have major impact on the early directions that a player's Garrison will take. I have seen graphics of the four sets of Armour available from the Dwarven Bunker in Talador as part of the Transmog 'perk' at Level Two, and this alone will have a very strong personal influence on my choice of Building for that zone initially. Similarly, taking the Lumber Mill for Resources in Gorgrond will give you a large boost to Resource generation, but with a 1000 Resource limit choices will need to be made on where and when you deploy its use. I will attempt to post some more details on this in the next week.
Thanks to Twitter, I am now aware that the Invasion portion of the Garrison 'package' is also live.
However, without the right set of circumstances to test it and with a currently bugged Garrison, I cannot offer any further insight than the fact it appears to be quite hard to play ^^ However it is good news that the feature is finally live, and I hope to have some insight into how it works at a later date.
Finally, before the wipe I was able to access a complete L3 Structure and discovered the Pet Menagerie feature for the first time. My good Twitter friend Liopleurodon has give this a once over, and I would suggest you take a look at her overview for more details of what this part of the Game will entail.