It makes a difference what kind of grass you have. Also, where do you live?

There is no reason to fertilize a cool season grass now, wait until the early fall. Warm season grasses you can fertilize all you want.

ZONE 7 - Long Island, New York. Not sure what kind of Sod it is. We hired a landscaper to install it.

Using synthetic (like Scott's) fertilizers, hold off until Labor Day. The weather is too warm right now.

Organics would be fine and sod is frequently spoon-fed at the farm. Milorganite is a good choice if you absolutely feel you must do something right now (actually, it's good in September and October in Long Island as well).

Both have their advantages. Synthetics are easier to use and the bags are smaller. Organics help prep the soil as well as feed the grass--and Milorganite contains a hefty shot of iron to encourage your lawn to turn a very nice green.