To add a little bit of detail... Typical operation at SFO is to use the 1's for as many takeoffs as possible. In the right wind, temperature, and load conditions, heavy jets can use the 1's just fine, even though they are shorter. Luckily, today the wind has been favorable for takeoffs on the 1's. This weekend, it was favorable for the 19's. Appears to have helped manage the volume. (And with 28R open again, it's even easier.)

Also note that some of the heavy jets taking off from the shorter runways this weekend were making fuel stops. (There's a thread in the Delta forum.)