So yet another Charisma-based arcane class? The Planeswalker class appears to be the opposite of Paizo's Summoner class in that it sends the character to other planes of existence, instead of summoning creatures.
One thing I've noted is the very limited number of spells known. Since its stated in the text that the Planeswalker needs to learn two spells of the same color to learn a higher level spell,most Planeswalkers will only have access to two colors at best. Was this intentional?