Comcast will likely get better customer retention, less service calls for higher quality netflix streams, a direct line to Netflix's core networking team to resolve problems, and a transfer of cash for the initial peering.

Comcast will also likely work with Netflix to estimate traffic growth and make sure their infrastructure scales before they have problems.

Again, we don't know the details of the deal. Assuming net neutrality was not damaged is also speculation. We need more information to know what is going on.

When Comcast has a packet that needs to get to Netflix, they can now hand it off directly to Netflix. That's all that peering means.