I think one thing to be careful about is not to read too much into response from your friends... they are already biased. That said, the difference within that set is interesting.
That makes sense...that was why we wanted to point out relative performance rather than absolute numbers. It is also probably fair to point out that the content and tone of our messaging differed quite a bit, which explains some of the differences.
There's a wealth of knowledge about email marketing which doesn't come up nearly as much on HN