First, in your combat phase, you turn a land into an Elemental X dork with trample and haste equal to this guy's power, so minimum 3/3
Its also nice to have a 0-mana sacrifice outlet attached to a commander, though this one isnt nearly as powerful as the likes of Yawgmoth, Thran Physician
This is a nasty addition to those decks as well a reason to push into those colors and a great Five-Color format win con too
At best, has a few options, but that's it
You might choose a commander who interacts uniquely with lands, like Soul of Windgrace, or Titania, Protector of Argoth
Summoners Grimoire is a bit less exciting, but its still a nice way to cheat out big Summons