Here's something I learned: don't be wishy washy. Avoid pandering to the person you're emailing - it takes up words and sounds pathetic. I've done this in the past and been the recipient. It just goes bad. Busy people work on short terse communication, unless they are actively in a conversation with you. And, in general, they will appreciate the first few emails you send them being of the same - condensed and full of…
I doubt Conway is that stupid to correlate email responsiveness with entrepreneurial ability, but on the other hand he probably appreciates prompt responses so he lets people believe that. Also, there's a pecking order. If you are some unknown founder who really needs Conway you should respond as fast as humanly possible. On the other hand, if Conway wants something from Steve Jobs he probably should respond quickly.
Which is not really what that point was saying.
I just think that the time between sending and email and a reply is not a good measure of how important you are to that person. Certainly, if someone replied within a few seconds of my email to them I'd have to pause and question why they responded so fast. Are they literally desperate for my input? Why? (of course, usually being desperate for that input is fine, and part of being excited to have a chance with someone who can really help you - but occasionally it is a marker of someone dodgy).
Basically: it seems something of a shallow way to judge things.