No, I'm wondering exactly how much more valuable the donation-matching pledge is than giving directly. If you'd rather do something else with the money than donate it directly (such as hold on to it to see if you can find something better), but you don't think that would be twice as good as giving directly, it would be important to know exactly how useful the donation match is.
It seems very unlikely to me that the expected value of donating to SCI is precisely between 1/2 and 1 times as high as the best alternative.
As of today, GiveWell has two new top charities:
1. Against Malaria Foundation
2. Schistosomiastis Control Initiative
Their previous top charity, Village Reach, no longer has much room for more funding. Which is a good thing: partly through givewell's influence they now have as much money as they can put to good use.