Xplornet "allows" p2p as far as they don't actively block it. Honestly, Xplornet is just a reseller, so they don't have much control over the network itself. I imagine the same for NetKaster, but if p2p traffic becomes a problem, I would expect them to throlttle you.
In all honesty guys, you can't compare wireless to each other unless you're in the same area as you would be on different networks and Xplornet has different transit providers for every network they have. If one network is having speed problems, that doesn't mean the others will.
Satellite, on the other hand, is a tricky call.