I've actually been super underwhelmed with Mortuary Mire in BfZ at least. You want to play it early, because it comes into play late, but you want to play it late, so you get value. And even the value you do get is relatively minimal - you need to have a creature in your graveyard that's on average better than creatures in your deck. I think it plays a lot worse than it looks.
In a low-curve format (like mine), Mortuary Mire coming in tapped doesn't matter so much if it's your 5th land and you're getting back an Obstinate Baloth or Archangel of Tithes next turn. It's an extremely useful card, and goes up in value the better your cheaper creatures are. It certainly does require a bit of thought as to when to time it and what to buy back, but I personally am happy to hold my 5th or 6th land drop for turns and turns if it opens up a great "trade" or acts as insurance on a key piece of my deck like Guttersnipe. I think it probably goes down in value if your format is Dragons Versus Hydras, but in a low-curve, tempo-oriented environment, I think it's fantastic.