P2P isn't very good for scientific applications, often the amount of data sent and received in cluster like applications, where using multiple CPUs across multiple computers, is very very small, otherwise it wouldn't be very good for that kind of application.
P2P is simply ideal for sending large amounts of data across networks when demand high and supply bandwidth is low. I also find it somewhat useful for sending huge amounts of data across LANs, it seems to be a more reliable system than something like Windows network transfer (300GBs+).