The filter lands
first debuted in Mirage. Then, they came into
play tapped, so you couldn't use the mana the
turn the fetch land was played.
Now, Onslaught gives
us the mana immediately, at the measly cost of
one life. These are great for any 2 color deck,
and might just be good for 3 color decks. In a 2
color deck, you can run 4 of the painland, and 4
of these. I see them getting a lot of play, and
many people complaining about mana screw when
they don't include enough non-filter lands in
In limited, they're
just as good. Even if you are only playing one
of the colors, play it. It thins your deck out,
which helps you draw more business spells.