When it is an Assembly-Worker, it is an artifact and can therefore be affected by spells and abilities that affect artifacts.

When it is an Assembly-Worker, it is still a land and retains all of its other abilities.

Any counters on the Assembly-Worker remain even if the counters stop being meaningful when it de-animates.

If an Assembly-Worker is changed to another land type, it will stay a 2/2 artifact creature and keep the creature type "Assembly-Worker" (until end of turn), but it will change its land type as directed.

Tapping a land for something other than mana is not a mana ability.

When animated into an Assembly-Worker, it has creature type Assembly-Worker.

The card name does not change. It remains "Mishra's Factory".

If another player takes control of the Factory while it is animated, that player keeps control until the control effect ends. They do not lose control just because the card stops being an Assembly-Worker. Note that Auras which steal cards will go to the graveyard if the permanent they enchant is no longer valid.

A noncreature permanent that turns into a creature is subject to the "summoning sickness" rule: It can only attack, and its {T} abilities can only be activated, if its controller has continuously controlled that permanent since the beginning of his or her most recent turn.

The layering rules have changed. Now if you animate a land and its power and toughness are lowered by Mutilate or a similar effect, reactivating the land's ability won't reset the values. This is because you apply all effects that set power and toughness to specific values before you apply any that modify power and toughness, regardless of the order in which the effects resolve.