Worth the money, but not without problems. Also not recommended for action oriented gamers.
The good things about this DLC is that it allows you to actually build your house in the wilderness, something that I personally have been wanting ever since I bought every house in the game. It adds loads more hours of gameplay, even if the majority of that is spent gathering the required materials for building your house. Adopting children was also something I was asking for, as I'm quite the hardcore roleplayer and I actually wanted one of my characters to actually have a family to go back to when he had finished adventuring for the day. The houses are also very big and once fully furnished will have a vast amount of storage space for your collectables.
Now on to the bad. The DLC seems to have problems when registering furnishings that you already have, sometimes misleading you into wasting your materials on something that is already there. Also, the architecture of each house is exactly the same and there's not many options when it comes to decorating the interior of your home. In my opinion, each home needed its own little style, just like the city houses already in the game.
Overall I'd say that for 400 Microsoft Points, this isn't a bad add-on. Bethesda said that with each DLC they wanted to add a new way to play the game, and as far as I'm concerned, Hearthfire does exactly that. As I've already said however, Hearthfire is not for action oriented gamers who would prefer slaying dragons and vampires to building houses and adopting children. It's more for the people who like a change from all the action and also like to have a few more roleplaying options.