I can also vouch for that for Peter's list and all the other lists that are over the 50% mark in the graph on my blog post. Quite frankly, it IS HARD to get this high of an open rate. Peter and all the other publishers who are able to do it consistently are somewhat of an anomaly.

That said, another way I've seen this done is I know publishers who will actively unsubscribe people who are not opening. And, this will give you a much higher concentration of people who consistently open...