You can vary the spices to suit your tastes. The ones listed above create a good base flavor. You can also add fresh spices or vegetables.
I'll often add a half onion or a few cloves of garlic instead of the onion or garlic powder. If you use fresh onion or garlic, make sure to put them in at the beginning and consider running the food processor a bit longer - up to 20 minutes. This will mellow the flavor a bit.
You can also add roasted peppers. I find it's best to add these toward the end when there's not more than a minute left to go on the food processor step.
You can make the hummus right away instead of chilling overnight. The hummus will taste fine, but I find that both the consistency and taste seem to be improved by waiting.
Remember it will thicken up a bit in the refrigerator, so it's okay for it to be a little bit soft after adding the water to the food processor. I find that 3/4 cup water is usually the right amount, but the exact amount varies a bit from batch to batch.
If you like very very creamy and smooth hummus, you can transfer from the food processor into a blender (ideally, a commercial grade like a VitaMix(R)) and blend for a few minutes. I usually don't bother with this, but sometimes I do, and some people seem to prefer it.