Text (LG+errata): All lands are 1/1 creatures that are still lands. [Oracle 1999/09/03]
Even affects Mishra's Factory by turning it into a 1/1 creature. The Factory can still use its ability to become an Assembly Worker. Any Assembly Workers already activated when Living Plane is cast become 1/1 creatures. [Duelist Magazine #2, Page 8]
Extended tournaments (see Rule 913) have always banned this card.
