Dude, its $5. You can barely get a meal at a fast food restaurant for $5. If Hearthfire added only 2 additional hours of play time it would work out to be $2.50 / hour.
In fact, it seems like the kind of DLC that will add literally dozens or scores of hours of play . . . IF you are the type of player who will use and enjoy it.
So in sum: if it sounds like fun to you, it would certainly seem to be worth $5!
This. Especially if you don't have a PC and/or like to try an alternative approach playing the game. If so, you could use Hearthfire as a means to an end (ie using it as a base for game completion of MQ/side quests etc) instead of just buying it to build a house in a straight game session. In which case, you'll possibly never want to use it afterwards.

It's great if you're an open sandbox gamer who wants to add new dimension and novelty to your game. If not, why not just add it and gradually build/collect materials for your home, while you attempt to save Skyrim from the Civil War and Dragon menace?
IMO the family & white picket fence theme adds some nice variety to the MQ & game play in general. So just think of this DLC as a nice break in character from your traditional giant toe eating, Fus Ro Dah shouting Dovahkiin.
