You can compare it to other programs and see if it's for you. Buy paying $450 to get $1500 seems pretty good - for the first year at least.
-- My mother has a Southwest Rapid Rewards Visa.
It had a threshold too - but I find that if you just charge everything possible to the card you'll do it easily.
Groceries, gas, restaurants, snow tires, Target runs - put it all on the card and pay the card off each month. I've used the card to buy a computer with and just gave her the cash.
She's spent enough on it to have "companion status" now where she gets to take a person free on any flight.