Ah, I hadn't thought of googling for a wattage figure...

Virgin says "Each pair of outlets at every row of three can support a total of 225 watts per this certification. When one outlet is drawing 150 watts, then the second one is limited to a maximum draw of 75 watts."

My heating pad says 70W, so that shouldn't be a problem. I can't imagine it causing interference. I'd just plan on leaving the other plug in our row for whomever has the aisle, and run all of our entertainment electronics off their batteries. (Or better yet, use IFE)