>> It's the open & click through rates that matter the most.
Absolutely. And I'll just add one more piece to that if you don't mind...
It's not just the click throughs from your email list I care about.
I want to know how many Uniques you can deliver from your full audience.
That's why I prefer to use "audience" as, these days, it's more holistic. You may have a hyper responsive blog readership, youtube subscribers, facebook fans, twitter followers... or maybe you just flat out have great advertising systems . Your "list" is great, but if you're promoting to your FULL audience (which may be the case if someone REALLY gets behind a JV), then it's your total uniques I care about.