With his first ability, you can start building your token swarm even without many other cards on the board
New Commander 2014 Green Guided by Nature
Having access to your best spell whenever you want it, and getting a body as well, allows you to close out the game incidentally, as a side-effect of cementing your control over the game
This comes back to the True ConvictionTrue Conviction debate, and I think the answers pretty clear: unless youre playing 40 nonbasics with Alpha dual lands mixed in, the mana wont be good enough
In exchange it doesnt come into play prepared, so you still have to work for it first
Theres just nothing quite like drawing more cards, and white has a lot of spells with that and other effects