Full Disclosure: I am a network ops engineer for Comcast.
Anyone who believes that buying private links into a providers network is the same as your traffic getting paid priority knows jack shit about network ops. In the case of Comcast, Netflix traffic gets no special priority once it's on the internal network. The direct links simply lets them bypass the naturally occurring bottlenecks that occur at internet peering points.
Now I'm sure a bunch of people (who are not network engineers) are going to argue over the wording and philosophy as to whether or not buying paid links into a providers network constitutes priority or not. It's not. In network operations, priority is a very specific concept. It means that you treat one class of traffic better than others, usually to the detriment of other classes of traffic. As an example, e911 voice traffic has the *highest* priority on the Comcast network.
Comcast does not treat Netflix traffic any better than anyone else's traffic. Nor is it treated any worse. It is forwarded as Best Effort within the Comcast network.
The only difference that buying direct links in meant was that they got to skip the congestion in the peering points. Comcast has alot more bandwidth internally and once traffic makes it into the network, congestion is not usually a problem (things do break, redundant links become saturated, etc. It's a big network, but in normal operation mode, congestion doesn't exist). What little prioritization we do has alot more to do with latency than with congestion (ie, your phone call is more important than your massive porn transfer, since voice is alot more sensitive to delay than bulk data transfer).