I suppose the discussion is what do you want from your exchange pt operator and what do you NOT want.

At the IXP level, "bits per month" always trumps "bits per second", and usually trumps "pennies per bit" as well. There are now a number of companies trying to sell wide area ethernet -- even some transoceanic but most just intracontinental. It doesn't work well for peering, though, just like SMDS and NetEdge didn't work well for peering. Too many moving parts and too little transparency.

Many people would not feel comfortable that circuit operators have visibility and maintain stats on even NUMBER of packets passed....

That's one of several important reasons why neutrality matters.