Cascade is easily one of the strongest abilities
in all of Magic. It's basically limited only by
the fact that the spells that have it all cost
three or more, meaning you have to wait some
time and can't take over a game on the second
turn without some additional help; in the case
of something like Maelstrom Wanderer, it's also
slightly limited by the large range of costs he
can cast via cascade and thus the inherent
inconsistency (it's not entirely optimal to
spend eight mana and get a Birds of Paradise as
your bonus spell). But this is a relatively
minor issue, as a free spell is always a free
spell, and even without library manipulation to
let you know what you're getting, a single use
of this card can put you too far ahead for
anyone to reasonably catch up.
An odd creature that possibly nets you two free
spells (provided one isn't a counter..), I'll
admit, it's hardly a great pick for a commander,
what with the casting cost, but it's green, so
ramp, yeah. It's a good fun deck pick though.