I really don't see what's so good about tsukoyomi. I tested it in my deck and it didn't do that much. Can somebody fill me in on how its good?

Its simple: Tsukuyomi+Thousand Eyes Restrict+New Rulings=Mass monster removal

You get Restrict out by Metamorphosis, suck up opponents monster, and then summon Tsukuyomi and flip TER facedown. The equipped monster is destroyed, then you flip TER, and suck up another monster. You get to potentially remove 2 of your opponents monsters each turn. Plus, you can...

Tsukuyomi+Magician of Faith=revive 2 spell cards in 1 turn, then get a spellcard back each turn. Flip MOF, get back a spell (such as Pot of Greed). Play POG (+2 card advantage) Summon Tsukuyomi, flip MOF face down, then manually flip MOF face up, get back POG and play it (now you got a 4 card advantage.)

But there is more:

Tsukuyomi+Mask of Darkness+Time Seal/Drop Off=Draw lock
Tsukuyomi+Morphing Jar/Needleworm=Quick Deck out

Well, you get the idea. Since Konami/UDE changed the rulings on monster battle position changes, this card has become godly.

well, if you've flipped MoF already that turn, you will not be able to flip her again that turn because you have already performed a manual position change of her that turn.

but you are getting the idea.

Plus Tsuky stops plenty of great monsters dead in their tracks. Jinzo, Pheonix, V Lord, and a CRAP LOAD of 4 star monsters all fall victim to her. Put them into defense and then either her or a monster with 1700 attack or so can take the rest. It also beats it's own lock. Tsuky takes out TER and things like Dark Balter or Senshi..which would normally be trouble.

It's strength comes in it's versatility.

I assume that using the last two combos you mentioned, TER would still need to be in play because otherwise, MoF/mask of darkness could get killed on the opp. turn, in atk position no less.

How would that work when you can't change the battle positions :p

Tsuku is generally a dead draw when topdecking, though. It also has a tendency to get sucked up in Morphing Jar #2s and Cyber Jars.

Great card, but be careful with it.

The combo is a great one, but remember the word "Yu-Gi-Oh" and "combo" do not work to well together. Surprisingly this combo is worth a mention or two, but a good duelist will be prepared to break this combo easily. I think the reason that it is doing okay is that people are not use to seeing this combo.

It is true that tsyku/mof/mask is a new kind of sick abuse. I believe that tsukuyomi should hit the restriction list. People weren't aware of her potential all that time, but now they are. So even if bls and jinzo or whatever gets banned, tsuku abuse will just be the next sure thing in every winning deck.